I'm not really tracking RD's post because when I read two pitch pitcher, I thought he meant fastball and slider and responded to that.
He has three pitches: fastball changeup slider. Lefties struggle with his slider because he manipulates the speed and dive based on count. He goes fastball slider to lefties. Leans on the changeup (his best secondary pitch) against righthanders. Touches 96 and is a big dude. Screams starter to me but haven't seen it addressed.
I may not have been clear. The fastball and change are his best two pitches. The slider is there as well, just isn't consistent with it. Developing that consistency with it will determine the ultimate upside. I've read it described as cutter like, and it's his main off speed offering against lefties.
Here's a blurb from Keith Law who had him outside his top 100, but named a few to watch just outside.
"Bennett is an extreme strike-thrower, with a walk rate under 5 percent and 68 percent of his pitches going for strikes this year, working mostly fastball/changeup. He’s 91-95 mph and comes from just below 3/4, getting slightly on the side of the ball to try to get more deception and glove-side movement to help him against lefties, while his changeup has some late tumble and gets a lot of whiffs from right-handed batters. His slider is a 40 without great spin or tilt, resulting in a reverse platoon split this year. Because of the command and chance for two solid-average MLB pitches, he offers a fourth/fifth starter ceiling; if anyone can get him to improve the breaking ball, though, his potential would increase substantially."