People already take into account how much they weigh, how familiar they are with alcohol, etc. when deciding what and how much to drink.

If I'm with someone who weighs about half as much as me and they drink three half pints while I drink three pints, I wouldn't treat them as though they were much more sober than me or expect them to treat me as though I was much more drunk than them.

The exception to the general Man/Woman presumption you mention even seems to have its own stereotype that gets used in various media: A man wakes up in bed with a particularly heavy woman, is ashamed, and has no idea how that happened.

That's probably more because “heavy” is what the “various media” usually use to signify something like ‘as sexually undesirable to the median man as the median man is to the median woman’.