SUMMARY
On Wayland, auto-hiding panels unhide when changing the screen resolution. They stay visible on the screen and won't hide again until the user interacts with them (i.e. moves the mouse over them and away again).

STEPS TO REPRODUCE
1. Set up an auto-hiding panel (and wait for it to hide)
2. Change the screen resolution (or, if running a nested KWin session, resize the inner KWin window)

OBSERVED RESULT
The panel unhides as if activated by moving the mouse cursor to the panel's screen edge. In contrast to the latter action, the panel will stay visible until the user interacts with the panel (e.g. by moving the mouse over it and away again).

EXPECTED RESULT
The panel should stay hidden when changing resolutions.

SOFTWARE/OS VERSIONS
Linux: openSUSE Tumbleweed (also tested Ubuntu 23.04)
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.105.0
Qt Version: 5.15.9
Graphics Platform: Wayland

ADDITIONAL INFORMATION
The behavior described in https://bugs.kde.org/show_bug.cgi?id=387252 sounds very similar:
> (Basically whenever a geometry change request was posted for the panel (e.g. implicit size of Task Manager changing due to items being added/removed) KWin would unhide the panel as it could have moved out of the visible are and become unreachable. It then didn't re-apply the auto hiding)

I tried debugging this myself for a bit, but the interaction between KWin/plasmashell is still a bit over my head :)