Even if you just straight up used NHLe to predict his point totals in the NHL for next season (D+2), which is highly suspect anyways, in 40 games he'd have 31 points but only 15 even strength points. Hischier has 21 even strength points in 40 games in his D+1 season, and even strength production has always been a better metric for looking at current and future success as you spend most of the game at even strength, and power plays are not always consistently strong from year to year.
Pettersson has a lot of talent, but he also has a lot of refining to do before he can be a well rounded NHL player like Hischier already is today.
It’s Nicos’ commitment to the two way game that landed him the 1C spot. He is doing his scoring damage at 5 on 5. If Pettersson can’t compete physically next year on those terms the melt should he get sent to the AHL to work on those parts of his game would be pretty funny. I’m sure he will be an excellent player at some point but he may become the cautionary tale for simple stat watching.