My issue with that is that Pixels are expensive, and in some places are not sold officially (meaning they can only be bought from smaller resellers with usually much less generous return policies). The newest models are outright unaffordable new. The only ones below $150 are either secondhand or out of support, so that’s what poor people are left with? Plus, no headphone jack.
I use Graphene myself, but I dislike absolutism. I don’t in the slightest regret buying my Pixel even though $300 is a painful sum to spend on a phone (and it was on the cheaper end if we’re talking about up-to-date models!), but I know that my mother would never spend this much on a phone - so I look into Divest or Lineage on more common and affordable phones.
Yeah, there is a whole “separate OS”, but, to my knowledge, there hasn’t been evidence of it casually being able to collect arbitrary data from the actual phone’s OS.