Easy way to test this:
- take a screenshot where the status bar is visible
- rotate the screen to landscape then back to portrait (do it 5 times so the elements drift for a significant amount of pixels)
- open the screenshot in Samsung Gallery
The status (and navigation) bar overlapping your screenshot should be visible, and you should be able to notice whether the status bar elements have moved their position. In One UI 6 they are static no matter what you do.
Screenshot from S23 Ultra running One UI 6. All status bar emenets perfectly overlap each other, indicating they are static.
Screenshot from Note20 Ultra running One UI 5. All status bar elements are moving, indicating OLED burn in protection is working.
This is bad on OLED screens as they will degrade uneven in that area. I have reported this problem to Samsung, but you should do it as well in order to raise as much awareness as possible so it gets fixed ASAP.
Note: Oddly enough, burn in protection works fine for the navigation bar.
Did you screenshot every time you rotated? Because I just did it 3 times on my OneUI 5 S23U, and on the third time it was the same as before, but the first and second rotate were both different.