The poophole loophole usually means something different. They say anal sex doesn't count as "losing your virginity." So they can have all the premarital sex they want, as long as it's in the pooper.
Additionally to what others have said it's also quite dangerous. You can drink a fatal amount of alcohol but your body will generally puke before it absorbs enough to kill you.
Using this method (boofing), you don't have that defense, it's absorbed too quickly and your body doesn't generally shit itself to expel poison.
Alcohol gets absorbed by mucus membrane much faster than by going through your digestive tract. And your anus is lined with mucus membrane.
It was a craze a decade or so ago where I live, cause teenagers did that to get drunk without having their breath smell of alcohol, and some of them ended up in the ER.
I see this so often now, I can't tell if people are honestly that dense or they're intentionally pretending to be. In the spirit of Fry and Andy Dwyer, I'm not sure I want to know the answer.