I would look at it like this: you spend definable amounts of time working out, eating, and sleeping while working towards your goals.
If you drink on PCT some amount of that time is wasted since you will diminsh your bodies ability to retain gains already made.
No one can tell you how much of that time is wasted but some of it is. Is it two hours? two weeks? two months? Who knows?
For me it is not worth it. I don't want to waste one minute of effort. I am serious about my goals so I quit drinking entirely. Attaining my goals is more important to me than a crappy buzz.
Just my two cents.