It is a pretty nice design, partly as a result of the fact that we've got a working system to look at (IPv4) and we have a lot more eyeballs "these days" (when IPv6 was designed, so, decades ago now) than when the Internet Protocol was a new idea.

I think perhaps the person you're responding to imagines that somehow DNS mandates a very naive implementation and so this behaviour would be incredibly expensive. The sort of person who sees a flip clock and imagines it needs 1440 different faces not 84 (or in some cases 72) because they haven't realised 12:34 and 12:35 simply use the same hour face.