Hmm, I got a different impression out of the interview; I took it more as "I've played man-to-man my whole life, but after a year of playing zone, people are starting to question whether I can play man-to-man, which is ridiculous" sort of. Of course, I haven't watched enough to tell whether he's been good enough at zones the year he played with that scheme, though being rational I wouldn't expect Stewart (nor any player) to instantly excel when switching into a defensive scheme he'd never played before. As for the rest, definitely agree that zone defense is a big deal for a big man, and zones in general will probably be on the up the next few years, especially against teams that aren't known for their shooting.
If Stewart is as good a defender as he claims he is, I'm interested. Above all in every prospect I've liked, I want defense-oriented play and versatility. I'd much rather stay put in terms of the playmaking and shooting that we have on the team already, and go for a defensive-minded prospect, than try to keep adding on to our pretty big list of players who excel on offense and need the ball in their hands to be effective. I'm looking at the '21 draft in terms of going for "that guy" who can run an offense and be the offensive engine of the team; no prospects in this draft that I've seen look to be able to get to that level, tbh.