Yeah, I'd agree about none of them being positive defenders at the next level....but when I'm watching these clips, none of them are really THAT bad. And tbf, I still think clips that show highlights/lowlights don't paint the full picture so I'll have to find some full games to watch.
Another way to look at this is that it's the opposite of what we often say about college offense. I wouldn't say that college basketball is "harder" to play than NBA offense, but there are things that we generally accept that will make things easier in the NBA. Having better teammates, better spacing, better offensive systems ect. But that flips on the defensive end. Because of the lack of talent, it's easier to defend on an individual level and especially in a team concept. The NBA prospect level guys can often struggle to create at this level because of X, Y, Z. When it's not an NBA prospect level guy, the offense is just hopeless and defense is so easy.
There's a lot of clips of them guarding individually in isolation.....but it's guarding a guy who is probably not that good and the paint is clogged and there are no shooters. And these guys are good enough to lock those guys down in that situation. Kon, for example, is obviously not a great athlete by NBA standards, but at the college level guys are like bouncing off his chest at any contact and he's not really that slow compared to his opponents. He's like a defensive wall when guys test him. I think it can bait you into thinking he might do the same vs pros, but it's just a whole different sport.
And it's even more extreme in off ball defense scenarios. You don't have to be great at closeouts. There's no mental energy required to stay in the possession. You won't find yourself in a situation where you have to zone up two guys to let the defense recover. It doesn't matter if don't navigate a screen.....I can go on forever about this. Individual defense isn't less important in the NBA per say, but there's this giant list of things you have to do in addition to individual defense that do not come up at the NCAA level. It really is chest vs checkers.