I don't think the .searchable in the bottom bar / glass look works when you have TabView that has NavStack.
BottomBar .searchable + Tab with Nav
Could you please share a code snippet that reproduces the issue.
The developer tutorial exhibits this issue nicely: https://developer.apple.com/tutorials/develop-in-swift/work-with-relationships
Correction: it does work when in the simulator, just not in the canvas / preview