After reading all the foregoing, I was reminded of a military pistol, maybe a Webley but not sure, where the magazine catch was two positioned. The purpose was to partially load a full magazine into the pistol and keep it in reserve while handling and firing the pistol as a single shot. Then, if the situation demanded, the magazine could be slammed home for semi-automatic fire.
Sounds like a completely absurb idea all the 'way around, to me. Now, I'm really curious, need to look that up again.