It seems Pi.Hole is aware of the ability to resolve hosts local to it. I would like to give it a list of networks or it just all RFC private subnets, the Pi.Hole will attempt to resolve them for it's logs and conditional forwarding.
All private IP ranges entered into a setting on the Pi.Hole will attempt to resolve any lookups seen from devices on these networks to domains. Reverse lookups seen for these private subnets are sent to the conditional forwarder.
Only hosts that are local to the Pi.Hole are resolved.