>The U.S. banking system lost $620 billion. Six hundred twenty billion dollars. That is a loss no less real than if money had been loaned out to borrowers who defaulted

Uh, no. That's just nonsense. If you lend money to a borrower who defaults, you immediately lose your principal and future interest, subject to whatever recovery rate you achieve. It's an actual, realized loss.

Banks have masses of unrealized losses on their long-dated Treasury holdings, but if you hold those bonds to maturity, you're going to get your principal and your interest.

It should be pretty clear those are Not The Same. The clue is in the word "realized", right?