I was recently confused by the UTM coordinate display in the status bar of the ArcGIS Pro scene view. I had a new project, and I set the default CRS to UTM Zone 10N because I was working on the San Francisco area. I switched the coordinate display in the status bar to show UTM coordinates and zoomed into my AOI. I was surprised and confused when the coordinate display said "10S ###### #######" (where # were some numerical coordinates).
I thought that maybe I had accidentally selected UTM Zone 10S (those were the only choices for UTM Zone 10). After talking to support, I was informed that there is another level of grid lettering in the Northern hemisphere called the Military Grid Reference System (MGRS). If I had looked at Seattle it would have said "10T ##### ######".
There is already another coordinate display mode for MGRS that displays the MGRS cell letters, so I think the UTM display mode should display the zone number and N for North or S for South, to follow the CRS naming connvention. Someone who wants to see the MGRS letters can switch to the MGRS display format.