If you're arguing from practice, the practical fact is that at least one
widely used DNS cache, the one in djbdns, doesn't return authority records
so clients can never find the zone cut.
Does it really not return even on SOA request?
Uh, perhaps this would be a good time to reread the RFCs and learn
what an authority record is.
Besides that as far as I know djbdns cache is not as used as much as
djbdns dns server itself and there are several small dns cache-only
servers available on unix that somebody who needs a replacement can very
quickly switch to ...
If we're going to demand that people change their working software, I
have a whole lot of much more exciting things to propose.
R's,
John