I definitely think there's room for improvement in card texts with this mechanic. Especially Transmogrify seems to be saying the opposite. I really like the new phrasings "gain it to your hand" and "gain it onto your deck". This makes it really clear, and should take care of most confusion whenever all cards get new wordings.
Transmogrify could be: "At the start of your turn, you may call this, to trash a card from your hand and gain a card to your hand costing up to $1 more than it."
Rocks could be: "When you gain or trash this, gain a Silver; if it is your Buy phase, gain the Silver onto your deck, otherwise gain it to your hand."
Hmm, but Empires is supposed to already have the new and improved wordings, so maybe Rocks will never be changed...?
Nomad Camp could be: "When you gain this, gain it onto your deck." (This would still not be 100% accurate, but this is probably impossible while still being understandable to most players. But it would make it distinct from the wordings on Watchtower, Royal Seal, Villa and Travelling Fair in a clear way, I think.)
Even more accurate: "When you gain this, gain it onto your deck instead of your discard pile." This has the added benefit of implying that it will be overridden by Transmogrify and Artisan.