iOS Simulator Safari JS PushManager.subscribe(...) empty keys

When I run the following code in XCode iOS Simulator on Safari (connecting via Safari DevTools):

navigator.serviceWorker.ready.then((reg) => reg.pushManager.subscribe({ userVisibleOnly: true, applicationServiceKey: "..." }).then((sub) => console.log(sub.toJSON())))

I get the response:

{ keys: { p256dh: "", auth: "" } }

But I'm expecting p256dh and auth (and endpoint) to be filled out. Why is it not?

iOS Simulator Safari JS PushManager.subscribe(...) empty keys
 
 
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