Yeah, it's surprising to see that the annualized rate is too high but the maximum term is only 28 days. I haven't tried the feature but OP, did you able to lend and made interest from your USDT? A test of 7 days is what I'm thinking with just a small amount that I can do for testing it.
Yesterday they borrowed all of the orderbook up to 730% yearly APY which is maximum.
Maybe this is the reason why there's a sudden surge for the orderbooks. I've calculated if you've got higher amount of USDT, you can make that much but I'm not sure if I'll do that with a huge amount. It is encouraging but I'm not confident.