Yeah, I've been using localhost domains on Linux for a while. Even on machines without systemd-resolved, you can still usually use them if you have the myhostname module in your NSS DNS module list.
https://www.man7.org/linux/man-pages/man8/libnss_myhostname....
(There are lots of other useful NSS modules, too. I like the libvirt ones. Not sure if there's any good way to use these alongside systemd-resolved.)