Not resolving 127.0.0.1 or RFC1918 addresses or even ULA for IPv6 is done to avoid DNS rebinding attacks. For most end users that is probably the correct move.
I agree that it’s usually the right behavior.
Sometimes I wish it would allow wildcards, but honestly that's probably just another way for users to shoot themselves in the foot (e.g. by adding '*').
pfSense for example uses unbound, and while it doesn't have a switch for disabling rebind protection, it does allow injecting arbitrary unbound config, which can disable rebind protection for any depth of a DNS zone or IP space. E.g.:
server:
private-address: 192.168.0.1/24
private-domain: plex.direct