Shorting tether can simply be a hedge against falling tether if you are holding large amounts. Doing that with stocks is completely normal and nothing to raise an eyebrow about.
I mean, why is being long $100k USDT and short $50k USDT at the same time better than just being long $50k USDT?
I don't have trading experience so this is not very intuitive to me.
Edit: oh, I think I get it. So if you were short $SOMETHING/$USDT then you're effectively long $USDT so if $USDT falls/crashes (i.e. loses its peg) even though $SOMETHING remains equally as valuable (as measured in other currencies), then you could lose a lot of money even though the underlying value of $SOMETHING hasn't really changed. So you could short $USDT/$USD to mitigate $USDT crashing when you're only interested in shorting $SOMETHING. I guess that makes sense?