I think he will be a very good player and missing him would be huge. It's not recent for people to say Franklin > Mustipher... they've been on that train for months, because that was apparently where the staff was pushing and they went and watched his film.
I do not care about "upside" and I sure as hell don't care abut SPARQ rating for a DT. PJ is a championship wrestler, and won DL MVP at his Opening regional. He has great size and plays very good competition and does not get moved off the ball. Is he overrated? Underrated? I don't know, but people around here think he's the real deal as an athlete and person.
If Franklin is so good why doesn't he have an offer from Maryland? Why zero Tier 1 ACC or SEC offers? Why rated as consensus mid 3

? Why did he not even make his All-State team much less All-Met out here?
Basically, either ND coaches know something that literally no one else does a la Will Fuller or people are overrating highlights that show a quick first step against bad competition.