Win11, i7-14700KF, RTX 4070, PL 7.4.0b151 here.
@Wolfgang has reported the same behavior in Update 7.4.0 b45, mask selectivity not usable anymore - #7 by Wolfgang . However, it works as expected in my case - mask is updated almost live, while moving chroma or luma without depressing the mouse button. Maybe the behavior depends on CPU/GPU?
Another thing pointed out by @Wolfgang – moving the control point hides the mask but displays the corrections “live”. You have to release the mouse button to see the new mask. This is good for me, maybe it’s bad for others. I use LA very rarely, so I don’t remember how it worked in 7.3.