Not sure if I'd use GrapheneOS even if it was available on other devices though. Really not a fan of the hostile attitude towards rooting when it's needed for basic functionality like backups — actual, reliable backups for every app, unlike those provided by the built-in solution.
What I noticed though is that Google often tries to upsell based on software features alone. For example, there is really no point in buying a Pixel 9 Pro instead of a base Pixel 9 as the hardware is practically the same except certain things. But Google markets the Pro model with more software based AI features. When installing GOS this really doesn't make a difference so one can always opt for the more inexpensive models.