I think a challenge of pixels and android in general is they don't seem to care about how well older hardware works with new os releases (or even some updates). I have an iphone se and it seems to work just fine after installing multiple os releases. Pixel type phones seem to struggle after a few os releases, as well as android in general. I should say I usually end up buying one generation behind cur on pixel.
So on top of google's short timeframe to allow 'next os release' support, apple does a better job on keeping older gen phones working well across multiple os releases.
This is one of the first generations of Pixel phones, maybe the first, where Google has had sufficient top-to-bottom vertical control over everything from the CPU on up to plausibly make this kind of promise. Apple got there before Google did, but Google may have finally arrived there.
Again, I have no inside info on this despite having worked for Google many years ago. We'll see what the announcement is on October 4.
So on top of google's short timeframe to allow 'next os release' support, apple does a better job on keeping older gen phones working well across multiple os releases.