Most likely because some "anabolic stuff" is a lot more harsher than others. While drinking while "on" is bad, I'd say drinking while taking orals is a sin. At least you're injecting.
Also personally, I'd prefer to stay away from someone who is taking tren AND drinking at the same time. Not due to health, but rather...higher probability to...extreme mood shifts...compound that with a low-carb diet...lol, everyone reacts differently, but that's a lot of things stacked against someone.
I also do not want to preach, but considering most "cycles" are a 6-8 week max (I imagine)...I have to wonder if it's really that difficult for some people to abstain from drinking for such a short period of time. I'd even recommend smoking weed over drinking during this time if you "need" to have a mind altering substance.
Having said all that, with no medical background, I'd pick vodka, lol.