This allows you to do more of the alcohol, even past where you would have normally stopped and this is OK up to a point, but if the coke wears off you get re-drunk far past you could have gone. It hits you like a brick wall. Shit goes bad fast.

Coke has a much shorter duration than either alcohol or heroin. Timing is key and can get complicated. Either 2 combinations of the three are already dangerous enough.Adding the other is too much.

But your point stands that things get grossly mis-classified.