I've probably answered my own question here, but wanted to confirm as I'm not 100% sure
I'm running the latest OpenWrt 19.0.4 as an access point only, shunting all DNS and DHCP requests to a pfSense firewall system. pfSense is running pfBlocker and is using DNS block lists that remap DNS requests to blocked sites to an internal address (i.e., 10.0.0.1).
Am I correct to say that as the upstream DNS request returns an internal/private IP, that this is the cause of the rebind log entry and that this is expected behaviour?
No real issues at present - the MR33 can be a bit finicky from time to time though this is likely related to the fact it has three radio antennnas that need to be carefully configured, which I probably haven't figured out yet!