Because of the nature of a couple of my apps, I’ve had them bounced for “providing commonly available services” (i.e. competing with OS tools). In each instance, I have appealed, citing some unique features, and have prevailed.
I think that reviewers have a number of “1-button” responses, provided by some kind of dashboard, in order to ensure a narrative is maintained. This is actually common for many customer interaction scenarios. I don’t like it, but understand why it happens.
I’ll bet that the more heated an exchange gets, the more “canned” these responses become, because...lawyers. He may, in fact, be communicating with a human, who keeps hitting canned response buttons (not much different from ‘bots).
I’ve wondered whether or not folks might use TestFlight for “shadow release.” I have seen app makers use Enterprise in that fashion. I have no idea (or opinion) on whether or not that was the case, here.
I’m not sure I would want to pursue my case in the court of public opinion. It’s a risky gambit, but this chap may feel he has nothing to lose.
EDIT: One thing that I should mention, is that I never have a release in TestFlight for more than a few days. It has a "time bomb"; I think, maybe 60 or 90 days. That means, in order to maintain an app in TF for three years, he'd need to keep re-releasing every couple of months. That speaks to some kind of intent.