Sure, most systems default to SLAAC which creates random long addresses. You can manually allocate them just fine and short addresses aren't going to cause collisions (and if they did, SLAAC handles it). Some of the networking people most (ab)using 192.168.x.y heavily are manually allocating them.

DHCP6 is pretty well supported on a lot of Enterprise routers, so the fd:: ULA space, which is what DHCP6 is most good for, has no required reason to be long addresses (outside of silly things like this link's mentioned Tailscale fingerprinting/advertising IP).