That's fair. Being blackout drunk is more than just memory impairment though - significant parts of the brain unrelated to memory also have impaired function during drunkenness. I would also suggest that there is a level of impairment where the impaired person lacks a sense of self while still being animated and seemingly conscious. This is what makes me think a blackout drunk person seems like a p-zombie (albeit temporarily).
(* - Not to be confused with the 'fast p-zombies' which were briefly popular in 90's existentialist cinema.)