what i could find...
What happens when you block unknown numbers on Android?
Block unknown numbers
This will block calls from **private or unidentified** numbers. You will still receive calls from phone numbers that are not stored in your contacts.
Unknown Caller means something different from No Caller ID, which indicates someone intentionally hid their identity. If you see the Unknown Caller label when your phone rings, it means your phone service provider doesn’t recognize who is trying to reach you.Oct 6, 2023
Thanks for the research 👍