Yeah I think that's a bit of hyperbole: the Pistons definitely haven't been playing Stewart like a back-up center, going from 21 mpg rookie season to 28 mpg this year along with the aforementioned 3-point attempts more suited to a defensive wing.
Maybe it won't result in significantly more wins, but a frontcourt of Wiseman at C a year removed from injury and Stewart at PF with his newfound shooting, Monte Morris at PG, Jaden Ivey at SG and Cade Cunningham playing point forward seems like a very respectable squad. And Monty Williams on his 2nd coaching job, which should help with the improvement of the "utes".
To this end, Detroit is doing the extension with the intent of locking Stewart in before "the leap(TM)" with the team around him improving. Sure it could be a gamble, but the team is not against the salary cap and in essence decided on him as the safest bet to extend now if they wish to stagger rookie extensions. When looking at bottom-line advanced stats (they aren't the same style of player) Stewart's output now is that he's essentially Grant Williams who got a 4-yr/$53 FA contract. I'd argue Grant has been handed a silver spoon thus far in his career with exceptional players at the top of the roster and he's much closer to his ceiling than Stewart. Still an overpay for a non-FA, but you get my drift...
I get Stewart is a "starter" on the Pistons, but he wouldn't start for the 29 other teams in the NBA. He's a "beef" Center & not even the best one on the worst team in the NBA. Jalen Duren is better now & holds more promise. Wiseman owns a higher ceiling. Is he better than Bagley & Livers at the 4? BUT if you believe Beef Stew is going to turn into "Al Horford" (suggested somewhere above) then it's a great signing. BUT I don't see it.
"Style of play" is critically important when assembling a team. The Grant comp is odd, GW can guard the perimeter while Stewart can't & nail a Corner3 at a high rate which makes him a nice complementary role player for Dallas. Stewart has flat-lined since his rookie year. He'd probably slot in as the 3rd string Center on the Mavs today.
League-wide, the back-up Center role is the one place where you can find value in the NBA. I'm really against paying 3-4yr money for them especially since the new CBA makes the
"its just the owner's money" argument now foolish. Detroit should be using its CAP space to add bad contracts & First round picks, especially 3 months before the start of the NBA season where more trades could occur (& they could play 3rd wheel). OR next Summer when many teams will be up against the 2nd apron.
Detroit is a "Respectable Squad", what does that even mean? If you believe that, then
Isaiah Stewart optimism makes some sense. Las Vegas has it right, Detroit & the Wizards have the lowest over/under win totals in the NBA at 25.5. They are firmly in rebuild mode but their GM & owner are in denial. Obviously, $45MM/3yrs gtd isn't crippling to any NBA team, but this contract & its timing is just one more small head-scratcher from Troy Weaver.