Yes, I cleared all caches. Chromium wasn't even installed prior. I also tried this on a Windows computer using the Edge browser for giggles, didn't seem to change anything. I may need to wait for leases to update again? I noticed one of my machines is returning its hostname, but none of the phones, other laptops, etc on the network are.
I would definitely renew leases. If that doesn't resolve it on all devices, you can add the client names in the Pi /etc/hosts file to map them that way.
Good point. It's not much use with dynamic addresses. I have everything that is routinely on my network on static IP's for that reason. I group in chunks of IP ranges so it's easier to read the pihole.log which shows IP addresses.
IOT start with .10. Wife's stuff starts with .30. Mine with .40, etc.
I seem to recall this worked before (it's been a while since I've used pihole for DNS) especially with pihole being the DHCP server. It should "just work" even for dynamic leases.