I think this would be expected though, no? Sure, there's flight to safety, but you're also reducing exports to the US, reducing the number of dollars flowing to foreign nationals, which reduces the demand for treasury bills, which an excess of dollars would often be used to buy to have an inflation-"proof" store for your dollars without currency risk. You would also expect devaluation of the dollar from tariffs / trade-war, which I would also expect to cause selling of t-bills in favor of local currencies