Tether has no such limitation. All the exchanges are complicit in this, wash trading is rampant, and there's an de facto central bank run by actual criminals. There is absolutely zero reason why iFinex can't take bitcoin to $100k or $1m or whatever they like. They only have opportunity costs.
The only thing keeping them in check right now is the appearance of legitimacy. If they were to overdo it, people might actually sell, which is not what they want. So until their legitimacy is tested (Jan 15) they will probably responsibly grind this higher. But on the last day, I expect billions and billions of USDT issuance so that they can run stops on every short in the market, collecting their last few shekels before the music stops and they vanish to an island somewhere.