Just wanted to post an update on this issue. After installing iOS 26 Beta 3, it appears this bug has been fixed.

The gap also appears at the top of the navigation bar in modal views that have a background color applied. This seems to be the same underlying problem as the landscape issue, but manifesting in a different context. I can also confirm that this is reproducible in the example project linked by the original author. Here is an image illustrating the gap I'm seeing in a modal view: