If you assume Tether is on the up and up: yes, this is absolutely correct. This also means there are $17B USD in a bank account somewhere, and you can go hand $1M in Tether in and get $1M USD back. Problem is, nobody has ever managed to do that.
If, however, you assume Tether is engaged in a conspiracy with crypto exchanges: Tether prints USDT and buys BTC from a friendly exchange, demand for BTC will go up when people see the difference between USDT-BTC and USD-BTC and try to arbitrage. Tether then sells BTC for USD.
Which is more likely? You can be the judge, but the fact that "exiting USDT for dollars" typically means "selling it for USDC" makes me pretty pessimistic about the first.
If, however, you assume Tether is engaged in a conspiracy with crypto exchanges: Tether prints USDT and buys BTC from a friendly exchange, demand for BTC will go up when people see the difference between USDT-BTC and USD-BTC and try to arbitrage. Tether then sells BTC for USD.
Which is more likely? You can be the judge, but the fact that "exiting USDT for dollars" typically means "selling it for USDC" makes me pretty pessimistic about the first.