I would not completely trust USDT, because they are not backed by anything. The DAI project is covered in real dollars. Trust in USDT is gaining popularity in the crypto community and over time it will become a postulate. So far, users have in their portfolio a set of different stablecoins.
That is my opinion on this matter also. I have the feeling that USDT is not totally backed with US dollars. When they admitted before that they are not fully backed, I have the feeling, that they are not always saying the absolute truth about their assets. So just be careful holding long term this stable coin.
Their asset could possibly be diversified to various investment which might equates to the total supply of USDT but that's still kinda hard to believe.
I mean, a company could grow their asset into this much of an amount $24 billion dollars within very short amount of time (half decade) is really crazy, If they don't got money from investment then I'd really feel suspicious about them. Still, I use it although only temporarily, holding money in form of USDT too long kinda feels dangerous.