`.toolbarBackground(.hidden)` not working

[dfabulich]

https://github.com/skiptools/skipapp-showcase/blob/main/Sources/Showcase/ToolbarPlayground.swift

In the Toolbar Playground, there's a "Hide Bar Backgrounds" playground.

case .hideBarBackgrounds:
    #if os(macOS)
    Text("Not supported on macOS")
    #else
    HideToolbarsPlayground()
        .navigationTitle($0.title)
        .toolbarBackground(.hidden, for: .navigationBar, .tabBar)
    #endif

On iOS 18, that makes the tab bar transparent; if you scroll up a little, it makes the collapsed navigation bar transparent, too.

On the "Medium Phone API 36" Android emulator, .toolbarBackground seems to have no effect at all. The tab bar is not transparent. and the collapsed navigation bar isn't transparent, either.

(On iOS 26, .toolbarBackground seems to have no effect. The tab bar seems unaffected, and the navigation bar is "transparent" by default, automatically blurring its background.)

[dfabulich]

This bug doesn't matter much to me, but I found it while regression testing #297, and I figured I should write it down somewhere.