yea, i guess that might be true... but, is it?
i have had a few d3 players that could have played d1. i mean maybe not starters at big6 schools, but really good players at mid majors. i have one on my d3 phelan team right now that (next year, when he's a senior) can really start for 85% of d1 schools and be a productive player.
so, how far off is that in real life? i don't think it's that far.
my buddy coaches in d2, they lost to an NAIA school the other day, and he said they had a kid who could play just about anywhere-- d2, some mid majors in d1, etc. there are kids in d2 who could play d1 but wind up going d2 for PT or whatever. a little more rare at d3, but there are a ton of late bloomers or guys that fall through the cracks (maybe off the court issues, grades, etc.).
basically, nowadays more kids are playing basketball at high levels for longer. everyone is playing aau for their entire career, playing bball year round, prep high schools are basically recruiting kids... it's a bit deal. so, there's a TON of parity. i don't think it's absurd to think that a solid d1 starter winds up playing d3.