It's ridiculous is what it is. It makes me deeply distrustful of the organisation behind Graphene that they would make such a crazy choice.
It is not ridiculous at all. GrapheneOS is not going to compromise the privacy and security of their users for the sake of spite for one specific company. It would be immature and irresponsible to make important choices based on spite rather than objectivity.
Motorola has stepped up to meet the baseline requirements for GrapheneOS support, and we should get Motorola devices with official GrapheneOS support next year.
The intersection of phones that have unlockable bootloaders, public-ish driver blobs and decent hardware is tiny.
What other phone would you pick?