Of course, this is the MM7 forum, so maybe you're right for MM7. Perhaps it's just a carryover from MM6 that didn't get converted under the new system.

But as Bones said, these values were all easily adjustable (you can go in and change it yourself using MM7View or MM8LE) to provide game balance.

It could still intentionally be left as physical damage for MM7, if for no other reason than to provide continuity.