Who is holding USDT? Likely traders who went onto Bitfinex (Tether's sister company) and sold their BTC there for what they thought was a good price. BTC, in this scenario, is a bridge to USD, because it can be moved to an OTC desk or a banked exchange and sold for cash.
So they're going to hold USDT until the crash, then re-buy BTC and move that out? Plausible, but it sure seems complicated.