"Most consumer combo gateway devices will do this by default as does Windows DHCP, but a lot of business firewall devices don't do it at all or don't do it by default.": Guess that explains it. I have a home router, but maybe its defaults are more business-like.

I'm pretty frequently in a scenario where I know local v4 addrs but not hostnames, usually on a network that's not my own. But even on my own network cause there's no simple way to discover the names, so not everything is a Linux box I can SSH into to ask the hostname. I'd use mDNS if I could reliably type something in to show all the DNS entries on the LAN, never having to diagnose any issues with this.