> But haven't tether explicitly promised to keep the USD reserves as cash?
Just as we think of bank deposits as cash, most accounting procedures (reasonably) treat Treasuries as cash.
I can imagine why central-bank-hating Austrians might not put money in treasury bonds.
Yes - sorry for being unclear , that was the 'almost' in my comment. I was explaining why this situation is unheard of and there isn't a standard practice, and why someone like Apple doesn't face this problem.