If google restricts access to its os, like they have already started, all you’ll have is pixel up to 10/11 still supported 10 years from now. They’ve already started by no longer providing device trees in aosp for their phones, so graphene has to work harder to obtain them now. Whereas if you work on lineage, you potentially have a greater number of vendors and potentially new ones ready to open up to draw in new userbase.
No, I mean, both graphene and lineage are based on aosp. But graphene supports only one vendor. Lineageos supports many, including google. Why invest in a vendor-locked os and risk loosing it all? I think lineage is a lot more logical choice. And I’m currently running Graphene on a pixel 8, after pixel 7.