Disc usage during programme restart phase of catalogue optimisation

Been waiting for lightroom to restart during the catalogue optimisation process for about 10 mins now.

Looking at task manager lightroom is still very active in background and accessing one of my HDDs. See below.

What is it doing? The HDD being read is just where photos are stored, catalogue is on a seperate ssd (L) which  back ups are written to as well .

Is it safe to shut down the PC during the period  Im waiting for lightroom to relaunch itself?

If this is normal behaviour?, shouldnt there be some indication that the programe is still active in the background during this phase of the process?