SUMMARY
When activating the Overview Effect or the All Desktops effect (unsure what it is called, when you slide down with four-fingers on a touchpad), panel blur is disabled temporarily. This is most noticeable with a touchpad and sliding up or down with four fingers to activate the Overview effect or All Desktops effect, but it is visible albiet briefly however these effects are activated (using a touchpad just allows you to activate the effects gradually). Using a background that provides a significant blur colour makes this even more noticeable, for example using the Plasma "Reef" wallpaper.

This was not present in 6.1.1 to my knowledge. This may affect other, er, effects that perform similar actions, but the Overview Effect and All Desktops effect are the only ones I am aware of.

STEPS TO REPRODUCE
1. Have a panel that has transparency and blur.
2. Activate the Overview Effect or All Desktops effect.
    a. This can be more noticeable when using a touchpad gesture that allows you to gradually animate the effects, and also most noticeable with a wallpaper that provides significant blur.
3. While the effects are active, there panel blur will be disabled. 

OBSERVED RESULT
These effects temporarily disable panel blur.

EXPECTED RESULT
These effects should not disable panel blur.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 6.9.7 Linux Zen
KDE Plasma Version: 6.1.2
KDE Frameworks Version: 6.3.0
Qt Version: 6.7.2

ADDITIONAL INFORMATION
May affect other effects, and so would be a more general bug than being specific to these effects. But as I can only reproduce it with these effects, I reported it under these.