Cat piss........any piss.....has ammonia-like smells, I don't know if there's actually something like ammonia in piss, cat, human, bear.......but there's also this combination of smells that say "urine". I don't think anyone would want weed that smells like urine......
And yes, weed that's stored too wet can develop moldy, ammonia smells. That's not something we want either.....
What might be the desireable "ammonia" smell would be "astringent"? Something that kind of hits the nose.......a little confronting, acrid, but again, in a "good" way. Not something that knocks my head back like ammonia and urine.
I think when strains are developed that are a real hit, like Trainwreck, Sour Diesel........they're a hit because they're unique. Different from any other strain, and noticeably different. Smells that are unmistakably THAT strain. If someone develops a strain that's LIKE Trainwreck, but a little diffetent, that's not special, that's not going to get it's own name. Calling it "Traincrash" isn't going to give it the stamp of it's own unique strain. Most people are just going to say "yeah it reminds me of Trainwreck, but......".