"But you're saying, Treasury issued a 2021 1099-INT in 2023?"

I read this as "received."

"Taxpayer received Savings Bonds from his deceased father."

The father dies in 2020.

"He got everything converted and redeemed through Treasury Direct."

Because three years later, he finally followed up? And up to that point, never checked the TD account to see these 1099s were available...I find it hard to believe they were freshly issued just now.

I sense amended returns in his future.