Actually, there are lots of (old) posts on that topic. You have experienced the correct behavior. Commercial can go to EDU, but not the reverse for 10 and below. I'm not sure about 11 - I think something changed there?
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB