Should have reasonably known is exactly how it works.
There are WRITTEN GUIDELINES. It is not in an OCA's sole discretion.
First, show me ANY source to prove that Comey released the CLASSIFIED memos, you don't even know that and are already speculating what he should have known.
Your argument is that an OCA has no legal obligation to classify and that the classification system is in the sole discretion of the OCAs?
Yes, most classifications except the ones specificied by Congress are discretionary
"Although most classification decisions are discretionary, Congress has required the classification of certain types of nuclear information. "
https://www.brennancenter.org/analysis/classified-information-what-you-need-know