One of the main goals of GrapheneOS is to release security updates as soon as possible, so if it's patched upstream GrapheneOS almost surely includes the patch.

Sometimes they even adopt pre-release AOSP security patch levels or backport security fixes from unreleased AOSP or kernel sources.

given that this is related to a hardware-ish problem (maybe firmware inside it?) in the GPU I'd bet it even affects it after the march update which was related to the bluetooth stack.

EDIT: Ignore me, I was confusing that with the recent blog post they had about finding an issue with MTE applying to all system apps too. Looks like GrapheneOS should have this as of their 2024030600 release because it brings in the "full 2024-03-05 security patch level"