In George Orwell's "Animal Farm", one of the rules written on the barn wall at the start, is
"No animal shall sleep in a bed".
Later two added words changed the rule entirely. Those words? Without sheets.
A's do this all the time, either adding to promises or removing a word or two along the way, until we can't recall the exact wording at the start.
Your AH said, "I will drink only every other weekend."
Wait a short while and if you remind him of this, the answer will be "I told you, I would drink only every weekend."
But you really didn't expect it would work this time anyway, so Saturday was a bonus.
God bless