DeletedUser301 It's up to the clock app in that case, which would need to support direct boot to be able to use part of its functionality while the phone is in BFU state. It's not up to GrapheneOS, but rather the app itself.
As an example of this, GrapheneOS actually contributed direct boot support to Florisboard, which means it can be used to unlock the phone while in BFU state where it otherwise wouldn't.