There are multiple facts that are hard to ignore about tether.
This "accidental" print is one of them. They have the ability to pump the price of Bitcoin and I think they use it from time to time.
Furthermore, there was an audit of their 1:1 USD to USDT claims that they "did" which wasn't very trustable - originally exposed by Bitfinex'ed I think. Not sure though.
All in all, Tether's either gonna be the death of crypto or the life of it. They have a lot of power.