Your SSA gov link says "The trust funds now hold only special issues, but they have held public issues in the past.". Any idea when the change happened?
“Any idea when the change happened?”
Good question—at least partially since 1985—this is mentioned in passing in this article:
https://rollcall.com/2023/03/02/obscure-law-contains-debt-limit-escape-hatch-for-social-security/
These scam artists are very sneaky.