NavigationStack with NavigationPath triggers multiple init/deinit of views in stack

TESTABLE CODE:

public enum Destination: String, Codable, Hashable {
    case cookie = "Cookie 🍪"
    case milk = "Milk 🥛"
}

final class Router: ObservableObject {
    
    @Published var navPath = NavigationPath()
    
    func navigate(to destination: Destination) {
        navPath.append(destination)
        print("||| Router: add to navPath: \(navPath.count)")
    }
    
    func navigateBack() {
        guard navPath.count > 0 else { return }
        navPath.removeLast()
        print("||| Router: remove from navPath: \(navPath.count)")
    }
    
    func navigateToRoot() {
        guard navPath.count > 1 else { return }
        navPath.removeLast(navPath.count)
    }
    
}

struct RootView: View {
    
    @ObservedObject var router = Router()
    
    var body: some View {
        NavigationStack(path: $router.navPath) {
            List {
                Button(action: {
                    router.navigate(to: .cookie)
                }, label: {
                    Text(Destination.cookie.rawValue)
                })
                
                Button(action: {
                    router.navigate(to: .milk)
                }, label: {
                    Text(Destination.milk.rawValue)
                })
            }
            .navigationBarBackButtonHidden()
            .navigationDestination(for: Destination.self) { destination in
                let _ = print("||| Destination: \(destination.rawValue)")
                // Method #1
//                anyViewFor(destination: destination)
                
                // Method #2
//                itemViewFor(destination: destination)
                
                // Method #3
//                cookieViewFor(destination: destination)
                
                // Method #4
                switch destination {
                case .cookie:
                    let vm = CookieViewModel()
                    CookieView(vm: vm)
                    
                case .milk:
                    let vm = MilkViewModel()
                    MilkView(vm: vm)
                }
            }
        }
        .environmentObject(router)
    }
    
    func anyViewFor(destination: Destination) -> AnyView {
        switch destination {
        case .cookie:
            let vm = CookieViewModel()
            return AnyView(CookieView(vm: vm))
            
        case .milk:
            let vm = MilkViewModel()
            return AnyView(MilkView(vm: vm))
        }
    }
    
    func itemViewFor(destination: Destination) -> ItemView {
        switch destination {
        case .cookie:
            let vm = CookieViewModel()
            let view = CookieView(vm: vm)
            let anyView = AnyView(view)
            return ItemView(childView: anyView)
            
        case .milk:
            let vm = MilkViewModel()
            let view = MilkView(vm: vm)
            let anyView = AnyView(view)
            return ItemView(childView: anyView)
        }
    }
    
    func cookieViewFor(destination: Destination) -> CookieView {
        switch destination {
        case .cookie:
            let vm = CookieViewModel()
            return CookieView(vm: vm)
        
        case .milk:
            let vm = CookieViewModel()
            return CookieView(vm: vm)
        }
    }
}

struct ItemView: View {
    
    var childView: AnyView
    
    var body: some View {
        childView
    }
}

struct CookieView: View {
    
    // MARK: Properties
    @EnvironmentObject var router: Router
    @StateObject var vm: CookieViewModel
    
    // MARK: - Views
    var body: some View {
        List {
            Stepper("Amount: \(vm.amount)") {
                vm.incrementAmount()
            } onDecrement: {
                vm.decrementAmount()
            }
            .minimumScaleFactor(0.2)
            .padding(.top, 12)
            
            Button(action: {
                router.navigate(to: .milk)
            }, label: {
                Text("Get \(Destination.milk.rawValue)")
            })
        }
        .navigationTitle(Destination.cookie.rawValue)
        .navigationBarBackButtonHidden()
        .toolbar(content: {
            ToolbarItem(placement: .topBarLeading) {
                Button(action: {
                    router.navigateBack()
                }, label: {
                    Text("Back")
                })
            }
        })
    }
}

class CookieViewModel: ObservableObject {
    
    @Published var amount: Int = 0
    
    let id: Int
    
    init() {
        self.id = Int.random(in: 1...1000)
        print("||| Init ☀️: CookieViewModel, id: \(id), num: \(amount)")
    }
    
    deinit {
        print("||| Deinit 🔥: CookieViewModel, id: \(id), num: \(amount)")
    }
    
    func incrementAmount() {
        amount += 1
    }
    
    func decrementAmount() {
        amount -= 1
    }
}

struct MilkView: View {
    
    // MARK: Properties
    @EnvironmentObject var router: Router
    @StateObject var vm: MilkViewModel
    
    // MARK: - Views
    var body: some View {
        List {
            Stepper("Amount: \(vm.amount)") {
                vm.incrementAmount()
            } onDecrement: {
                vm.decrementAmount()
            }
            .minimumScaleFactor(0.2)
            .padding(.top, 12)
            
            Button(action: {
                router.navigate(to: .cookie)
            }, label: {
                Text("Get \(Destination.cookie.rawValue)")
            })
        }
        .navigationTitle(Destination.milk.rawValue)
        .navigationBarBackButtonHidden()
        .toolbar(content: {
            ToolbarItem(placement: .topBarLeading) {
                Button(action: {
                    router.navigateBack()
                }, label: {
                    Text("Back")
                })
            }
        })
    }
}

class MilkViewModel: ObservableObject {
    
    @Published var amount: Int = 0
    
    let id: Int
    
    init() {
        self.id = Int.random(in: 1...1000)
        print("||| Init ☀️: MilkViewModel, id: \(id), num: \(amount)")
    }
    
    deinit {
        print("||| Deinit 🔥: MilkViewModel, id: \(id), num: \(amount)")
    }
    
    func incrementAmount() {
        amount += 1
    }
    
    func decrementAmount() {
        amount -= 1
    }
}

@Knyhuus an identical function similar to what you have in the scope of the .navigationDestination(for:) closure would be:

    @ViewBuilder
    func itemViewFor(destination: Destination) -> some View {
        switch destination {
        case .cookie:
            CookieView()
        case .milk:
            MilkView()
        }
    }

Secondly, StateObject property wrapper should be marked private and instantiated with the View.