Let's assume that it's correct that "no one who was not immunocompromised should have ever taken it." (It's not, but let's assume that it is)

Was this knowably true in Q1 2021?

Can you please share the specific, contemporaneously available information that made this knowably true?

If you can't, then it's not "sunk cost" infecting someone else's thinking, it's hindsight bias infecting yours.