The difference here is, if you're on another interface--say, Palnet--then you earn that token for your curation. You don't earn STEEM. Unless I'm missing something. The tokens on the Ethereum platform don't take anything away from ETH. If you earn a particular token on the Steem blockchain because you're using an interface other than Steemit, then you are earning that token and not STEEM. That takes STEEM out of circulation.