After running the Rebuild Maven Repository Metadata task, I refreshed to see the status and noticed it said "Unknown running".
This appears to be the default return.
Analysis from Brad Beck [X] states the task may be STARTING and suggestion is to add a state for that.
I feel like this may be a recent change but maybe just unlucky timing on my side. I did not check older NX3 (task (re)added in m4) or NX2 at this time.
I waffled between Bug and Improvement; bug for now but made it trivial.
Debug was off when I noticed this.