Bullshit. Sure, raw athletic ability helps, but isn't the end-all, be-all. Give Tony Bennett at Virginia the Iowa roster for a month. Of course I can't promise you… but I promise you Bennett would have these same damn dudes defending the 3 fairly well. Maybe not best-in-the-nation well, but well.
Seriously. Watch Virginia. Kyle Guy is 6'2" 175 combo guard, primarily the 2. He's a little longer than Bohannon, a little more athletic overall, but pretty similar. Kyle Guy is a joy to watch defensively because you can tell how well coached he is, how he's bought in. And he's definitely a scorer's mentality type of player. But he's defending his butt off. He gets by with constant preparedness, never falling asleep, anticipation, very active hands and feet (especially hands) both on the ball and off the ball, and he almost always boxes out. Thing of beauty how the shot goes up, and he finds his man and puts a body on him — even if his man is at the 3-point line. That's coaching. Primary ball-handler is Ty Jerome, 6'5" 200 lbs, very similar athlete to Moss, appears to be stronger in the core given how he never falls down as does Moss. Very similar athlete otherwise. Jerome does everything Guy does on defense. You can tell they're coached by the same staff. I could do this for nearly every player, make a reasonable comparison to someone similar on Virginia's roster. But I'll stop here.
Yes, better athletes help. Recruiting helps. Gesell and Sapp were better defenders regardless of who coached them, Fran or Bennett. But coaching, really good coaching, can get a lot out of an otherwise "average" or even "below average" athlete. Going back to Guy and Jerome from Virginia — neither of those guys scream "superior athlete" yet they are definitely above-average defenders.