I've seen this cited as a reason for expansion before, but I've never been able to find such a rule/policy...feel like it's a myth. If it's true, it must be a football-specific policy because there are other sports like lax where there are more autos than at-larges.
Regardless, there are currently 11 auto bids, but that should drop to 10 next year since the OVC and Big South are combining their football conferences since MVC is losing Murray State and Big South is losing NC A&T and Campbell. I assume the WAC-ASUN partnership will have to continue as neither will have enough on its own for an auto again.
Anyway, I don't really have a problem with the current size and conferences like the PFL getting bids. They're still part of the subdivision and it's a bit like hoops...the 15- and 16-seeds are almost always going to get killed, but every once in a while they pull an upset. (I do recognize the difference that PFL is non-scholarship while at least in hoops everybody is playing with the same number of scholarships.)
What does throw a wrinkle into things is the bye system. With fully a third of the teams getting first-round byes, those PFL teams are not getting matched up against the cream of the crop and instead it's a "mid-tier" qualifier like us who benefits from the matchup. You can consider Elon and us as having very similar résumés, yet we got a cakewalk while Elon faced what the polls said was an equal in Furman.
The other issue is that the PFL is really an outlier with their non-scholarship status, so whoever gets matched up with them really lucks out. You might put NEC and perhaps Big South in a similar but slightly higher bucket, although even their champs played some respectable games against quality OOC foes (including Saint Francis against us).