Yes, it is still an issue.  The behavior is the same in 6.3 (both estudio
X server Xsun each use about 20% of the CPU when moving the mouse continuously).
No change from 6.0.

There is also a new problem, where estudio uses CPU continuously even when
I am not doing anything with it.  I think there was a change to event loop
handling or something so that it now uses polling.  Each instance of
estudio now uses 1-5% (varies) continuously when it is just sitting there
and I'm not interacting with it at all.