While Tether is certainly opaque (you could say shady), it's incredibly doubtful that it's unbacked to a significant extent. Even if it's only backed at 50% (which would be really shocking to me), it would take 39B$ to flow through the system to actually cause a depeg. That's very unlikely, and just the logistics of it means it would leave a lot of time to Tether to clear the air.
Consider that being "nakedly" unbacked (no underlying assets) in any meaningful capacity would qualify Tether's leadership for a quick trip to prison — as they've repeatedly said they were fully backed.
The real risk is them sitting on "commercial paper" (short term debt) that is now worthless or significantly discounted. I still doubt they would have lost more than 50% of reserves this way.
I think it's also interesting that SBF (FTX's founder) is fairly confident in Tether (of UST he said months ago "we know how this ends"). He seems better informed than most, and it seems unlikely to me he'd stake his company (which has extensive dealing with Tether) on a system that cannot be sustained.
I have no chip in this fight, and honestly, I do agree Tether is riskier than alternative, which is why I've never even held it. But UST and Tether are vastly different beasts in term of risk profiles.