I’ve installed it on my personal PC and my laptop, and in both cases it seems to have caused the return of the performance slowdown - 6-10 seconds to load/switch jobs in Job Entry. The good news is that it seems that applying the fix from Microsoft seems to be working effectively to resolve the performance hit now with 2021-04 (KB5001330) installed, on these two machines at least. Seemed to not work as well on 2021-03 cumulative update for whatever reason, but maybe I just needed two or three reboots for good measure. 
Curious to know what others have experiencing with this update.