SUMMARY
When using the overview effect, any window that crosses the border between two screens (i.e. it is shown on both) is shown twice. 
This can be quite confusing, especially when trying to clean up the mess of windows you have, and could lead to accidentally closing a window because you were thinking it was there twice.


STEPS TO REPRODUCE
1. Drag window to be partially on one screen and partially on another
2. activate the overview effect

OBSERVED RESULT
said window is shown twice, once on every screen that it was partially on


EXPECTED RESULT
window is only shown on screen where most of it was on

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux Stable, latest updates
(available in About System)
KDE Plasma Version: 5.25.5
KDE Frameworks Version: 5.98.0
Qt Version: 5.15.6

ADDITIONAL INFORMATION
I have recorded a video, but it is too large for me to attach it, so here is a direct link to it: 
https://cloud.felixfischer.tech/apps/sharingpath/felix/shared/2022-10-03%2021-02-51.m4v