I have experienced the same behavior. There was an instance or two where I see the caller ID name of a business that's calling and then within about 1 second it disappears and only the phone number shows. Lately I have never seen anything but a phone number unless it is in my Contacts.
I assume using the Google Dialer app would resolve this but considering caller id info has shown up briefly I wonder if there's a bug in AOSP or GrapheneOS in this case.