In my experience most DNS admins abhor the idea of putting private IP addresses in public DNS space and it's simply not even an option they consider. I've used weird DNS tricks like this for years and never really encountered any issues, though. I currently have both my wireguard and private IP networks published to public DNS to make my life easier, for example.
I allow it. I use A records to set individual subdomains of my personal domain to individual Tailscale IPs. Then, when Tailscale is connected, all is well. Is this worth a telling off?
Private IPs should not be publicly routable. For one, you are no longer standards-compliant. If you want to depend on the IPv4 standard, you've already broken what you're trying to depend on.
