Stunting is actually easier to learn than tumbling point blank. You don't learn level 6 in HS or all star so any team with freshman on it have girls that are literally learning those skills for the first time. I don't have a full but I can do collegiate stunts. I've seen girls master an elite college sequences in one day, without prior experience. Tumbling is a build up, and frankly progressing from a bhs to a full in college is RARE.
You also can't win if you have elite level 6 stunts and no elite tumbling.
I agree with the sentiment for sure. A good coach can take any team and get their stunting up to snuff - collegiate cheer is filled to the brim with girls from HS programs that only did straight up libs and guys who switched from football their freshman year of uni and who are now doing rewinds and full around 1-1-1's. But the reality is it's much rarer to get people from this situation and to be able to teach them to full. Getting them to tuck, or to do what NCA considers a layout, is much more realistic.
Also, granted I'm biased, but as someone who has competed intermediate and advanced, the biggest difference really wasn't stunts. Both teams did a full around, only one walked a half and one walked a quarter. Both teams did a release move. Both teams dismounted (full/double downs are all the same on my end!). And both teams did an inversion. Clearly a rewind and a fake handstand up are different, but I think a good coach could get people to do either.
Baskets are kind of moot when comparing imo. Kick doubles take a lot of body control to do well and can take longer to learn than easier inverting baskets like Arabian fulls or bird fronts. Plenty of girls (who have learned on my skinny but!) throw inverting doubles on boys without having much body control, but by lifting, dropping the shoulder, and pulling while the front throws toes. But, regardless of intermediate or advanced, all star girls tend to have an easier time for obvious reasons.
Pyramids, like stunts, are difficult in different ways and it mostly comes down to coaching and proper progressions.
Ultimately I think comparing them is a little apples to oranges. That being said, I think tumbling is their biggest difference. I always said that if you dont have a full, you're an intermediate athlete on an advanced team. A good coach and proper progressions can turn most any team into an advanced stunter in a season or two, but few people can be tumblers in that amount of time.
Because of that I don't think UCA would really benefit from an intermediate division.