Obviously it does not follow that if it is not written that they were OK, then they were not OK. They could have said they were not OK, and they could have refused to add the miles to the AAdvantage accounts. As it is they accepted it silently for many years (thus implying consent---it's not as if the bonuses were added to AAdvantage accounts by hacking them) and then declared that this violated some vague and general criteria with retroactive effect.

I recall hearing that in the old Soviet Union you could be charged with crimes but never told what they were---you were supposed to know. This is somewhat similar.