IMO orphan kernels are not Linux. If it can’t update with mainline, it is a sterile mule. So no, even as an avid user of Graphene, it is not Linux because google has stollen ownership with an orphaned kernel using proprietary and publicly undocumented hardware.
In this vain, no mobile chipset or radio modem has been FOSS or Linux in a very very long time if ever. Like the last radio that was fully documented was the Atheros stuff, and the last processor to come close to fully documented is the stuff Leah Rowe supports in Libreboot and that is only because of her hacking skills.