I imagine there's a lot more money to be made making someone pay for the fees and costs of a repo, than a phone call asking them to pay a few dollars. Although his friend could also be lying about the few dollars part.
General industry practice people are put in delinquency buckets, and generally not by amount but in the 'are they past due or not?' I'm speculating but there could be other behavioral scoring as well and if they just automated the process of dispatching well... that's on them and good luck with that overhead.
I know he had to pay much more than the under-amount: fees & whatnot. So I'd assume that GM Finance cleared a profit on this deal.
Yeah, on the repo man accepting payment: I'd almost believe that happened, and he just pocketed the money & reported the car missing.