I was wondering why one of my Hungarian 37M magazines was only holding 6 rounds of ammo, as opposed to the standard 7.
Well I discovered disassembling it, along with my P.37 magazine, and another 37M magazine, that the two models have different length followers and my one 37M magazine has a P.37 follower in it! Perhaps it was replaced at some point or it was a mistake at the factory as the two models were being made concurrently.
So the P.37 follower has a longer back extension, thus bottoming out sooner in the magazine body. I did a little experiment and you can in fact get eight 32 ACP cartridges in a magazine with a 37M follower but it was a little tough getting the last round in so perhaps they wanted to retain the 7 round capacity to avoid potential feeding issues with an 8th round crammed into the magazine.
Yes it seems at the end of the day the rationale was to keep the round capacity (7 rounds) the same between both magazines and cartridges. Though with a little tweaking they probably could have gotten 8 rounds in the P.37 (32 ACP) pistol.