The same thing happens for me (HXFX, 3.71). I have two snapshots created and named. When I enter snapshot mode (bank up+down) they both names show properly. I set up foot switch one using command center like so:
snapshot 1 - press/release press = snapshot 2, release = snapshot 2
snapshot 2 - press/release press = snapshot 1, release = snapshot 1
When I press FS 1, it does indeed toggle between the 2 snapshots as intended, but the scribble switch always just says "snapshot".
Another weirdness is that it seems to be necessary to make both press and release go to the desired snapshot. I originally set release = none, assuming that meant nothing would happen on release. But instead, when release = none it takes two presses of the FS. First press does nothing, second press toggles as intended. I don't understand that at all.
Maybe it's worth mentioning that I set everything up using HX Edit, not on the unit itself. That includes both the command center stuff and the snapshot names. The snapshot names do show correctly on the scribble strips when in preset select mode.