What a weird take. I see it the other way round: if you can run GrapheneOS, run GrapheneOS, period. If you can't, then there is a really cool project called LineageOS that you probably can run, and you should look into it :-).
Yes this is probably a good summary. If you have a fairly recent Pixel, there is probably no reason to pick Lineage over Graphene. But Lineage covers far more devices and device types, including ancient ones.
It's not quite that simple. I don't use GOS because GOS and I have mutually incompatible views of user control. I prefer that I control my phone, they say I can't be trusted with that.