It's yet TBD determined whether or not Trent and Duval won't 'sniff' the first round. I don't even know your basis for that argument. From one or two mock drafts? I could show you 10 that say the opposite. Besides, until the combines this argument, for either of us, doesn't hold much weight.
Duke isn't creating the culture. It's a culture that's existed for quite a while. Some kids are just different. Grayson Allen could have left and been a first-round pick two years ago. He wanted to be at Duke. Harrison Barnes would have been a lottery pick after his freshman season. He wanted another crack at UNC. Maybe Kevin Knox feels he has unfinished business and isn't ready to give up being a kid yet?
The plan in both the Duval and Trent camp's has been to go pro right now. Can that change? Certainly. But I don't think it's very likely. I can't speak to Kevin Knox because I didn't follow him whatsoever, other than the three or four games I saw UK play this season.