"Negative caching was an optional part of the DNS specification and deals with the caching of the non-existence of an RRset [RFC2181] or domain name."

Optional.

Now, I know how DNS works and so do you but your average sysadmin wants instant results as they thrash around trying to get something to work. You see the same effect with firewalls. If state tables don't get flushed after a change then the change will seem to be ineffective. Been there and done that. States often die after five minutes and so do Windows DNS fuck ups.

That is why the master says: "wait longer" followed by "turn it off and on again" or "go out and smoke a fag" or "get me a coffee" or whatever. When your arse is on fire in IT, learn when to trust your judgement and take five.