No matter what size of simulator you use on any Macbook from any year, the screenshots are completely unusable on app store connect. App store connect requires extremely obscure, uncommon, and illogically sized images for screenshots. If you take a real screenshot on an actual iPhone 13 then try to upload that image it will also no work. Will Apple ever make software that properly works with its own development software? Will Apple ever make it so the simulators screenshots are properly sized or will apple allow for appropriately sized images to be uploaded for screenshots?
Funny enough the best way to get around this problem is to use a third party conversion app to make up for apples extreme inadequacy and purposeful stifling of innovation and invention.
Apple should take a note from the people they are keeping their boot on the neck of. It is elementary practice to resize images on devices and in widgets. They are forcing these crazy restrictions due to sheer laziness and lack of ability.