"....i'm an old fart, but i worked on a lot of those in the 60s-70s. DISCLIMER: i'm digging this out of my distant memory in a foggy part of my brain......"
Your explanation sounds right from what I remember. And yes I remember them, never read them just knew you had to do it. Even remember why. A generator is self energizing, but relies on a slight magnetic field in the housing to get started. Polarizing sets up that field.
A few years ago I was doing a fair amount of work on old Harleys had a couple brought in by guys who had changed their generators but still wouldn’t charge. I polarized them and cured the problem. They were pretty amazed about what could be done with a jumper wire