Why is Stage Manager M1 iPad Only?

Flashback to WWDC 2021, and tech twitter and tech YouTube were livid — borderline apoplectic — that iPadOS 15 didn’t deliver any new features that took advantage of the M1 chipset Tim Cook had mission-improbable’d into it just 2 months before

Flash-forward to WWDC 2022, and tech twitter and tech YouTube are every bit as livid, as borderline apoplectic, that iPadOS 16 has just delivered exactly that kind of feature, a feature that requires M1 — Stage Manager

So... why?