Bug 457601

SUMMARY
When a window opens already maximized and you attempt to drag the window out of that state, the top left of the window will be positioned under the cursor instead of where you initially clicked and dragged from on the title bar. The cursor's position is correct, but the window itself is moved to the position stated above. It affects Qt and GTK apps, but outside that I'm not sure (Discord and Spotify aren't affected for example).

STEPS TO REPRODUCE
1. Start an application/Open a window in a maximized state
2. Click and drag the window from anywhere on the title bar until it exits maximized

OBSERVED RESULT
Top left of window ends up positioned under the cursor regardless of where on the title bar you clicked and dragged from.

EXPECTED RESULT
Replicates the behavior consistently seen in X11, where the window "restores" relative to where you dragged the title bar from.

SOFTWARE/OS VERSIONS
Linux: Up-to-date Arch Linux
KDE Plasma Version: 5.25.4
KDE Frameworks Version: 5.96.0
Qt Version: 5.15.5

ADDITIONAL INFORMATION
I tested various scenarios to see what makes it behave correctly again and what doesn't. Here's what I found: 
- drag from and back to maximized without letting go: BROKEN
- drag from maximized and let go, double click the title bar back to maximized: BROKEN
- drag from maximized and let go, drag the window to the top to maximize again: FIXED
- drag from maximized and let go, resize window, double click title bar or drag window to the top to maximize again: FIXED
- double click the title bar into windowed, double click the title bar again back into maximized: FIXED