That generally works, although in some cases it makes a difference whether two hosts are on the same tld; at the very least, it implies a connection between the two that may not always make sense (why is aggressor.example.com attacking victim.example.com?).
The same goes for TEST-NET (192.0.2.0/24), TEST-NET-2 (198.51.100.0/24), TEST-NET-3 (203.0.113.0/24), MCAST-TEST-NET (233.252.0.0/24), and the IPv6 documentation-only prefix (2001:db8::/32).