It's really pretty simple. In the Indiana game, he hit three of his shots after Iowa was down by 24 with 6:25 to play. The game was already decided at that point. He also had a couple more in the second half when Indiana held a 15-20 point lead, but it was early enough that you could argue the game wasn't decided (but a comeback against that IU team on their floor was unlikely). He hit 5 threes against MSU as a freshman, but four of them came after Iowa was down by 26 with 5:34 to play. Against Clemson, all three of his made 3-pointers came after Iowa was down by 22 with 9:58 to play. Against Creighton, all three of his made 3-pointers came after Iowa was down by 30 at the 10:26 mark.
Statistically speaking, those four games made up 21 of his 45 made 3-pointers, and most of them were hit in garbage time. The "he doesn't hit big shots" narrative didn't come from nothing. Of his strong statistical nights as a freshman, the only game where he didn't seriously pad his numbers in garbage time was the Northern Illinois game (hit three treys in the first half). Then last year, he didn't hit much of anything at any point of the game.
Yesterday, all of his 5 threes came in big spots. He didn't keep raining threes after Iowa took a commanding lead; he rained them when we were down by 9 and up by 6. He kept hammering home dagger after dagger, which isn't something he did in his first two years.
It can be tough to draw a definitive line between what counts as a shot that matters, but in the case of his best freshman performances and his last two performances, the difference is pretty clear. Kind of like when you debate on how far over the speed limit is acceptable. That's sometimes tough to figure out, but you know that 30 over is probably a bad idea.