Summary: It needs to be a BLOODY good session before the 12 hour rule is inappropriate.
Most people after drinking as heavily as that would have a very disturbed sleep, and would have plenty of residual by-products of alcohol breakdown still in the bloodstream. It is these by-products of alcohol and disturbed sleep that give you the hangover and and degraded performance the morning after, rather than the alcohol itself. So although you might not have any more alcohol in your blood, you would probably not be at full performance.
The nasty by products of alcohol can hang around degrading performance for a long time depending on various factors. In the days when I was a fairly serious rower (rowing with oars, not fists), after a bit of a drink it would sometimes take three days before my erg times were back to their peak.