I was about to start a new thread on this. I'm seeing wild inconsistencies on Jamf School for this as well. I've set it for one user or I've set it for allocated storage of 2,3,4,5 GB and yet the device itself reports 15gb have been set aside for that one user. JS reports one user with 17GB for that user. Confusing as all get out and what's worse is that after each successive wipe of the device the storage reports differ, not wildly but differ nonetheless.
I use shared iPads with temporary user for forgetful students or other purposes and up until 14.5 it's been relatively stable and consistent on the management side.