Or maybe the "HAM" usage might've referred to "Copper shading" for the horizon/background? I haven't played it to really know either way,though!
Although speaking of "HAM" screens I think I once read that the Amiga version of the PC Golf Game "Links" used the HAM mode, which would explain why it was terribly slow.
The most active use that could've been made of the HAM mode would've been in digitised images,(All the poker games!),I guess!