I can tell you for a fact it happens. I lived in Orlando for 18 years and it is definitely a thing that the younger crowds like to do, whether its called "Drinking around the world" or "Conquering the world one beer at a time".
Its like a contest, heck they even have shirts for it. They usually do not arrive til later in the day at EPCOT, so they are not in the heat all day. A couple of years ago one of our friends said that he and his wife had to go pick up their son and his 3 buddies from EPCOT, they were not smashed but smart enough to know not to drive. I guess the one guy who was suppose to be the designated driver only lasted a couple of worlds
We have gone 4-5 times during F&W and have not seen anyone vomit but have seen our fair share of unbalanced, stupid and sometimes load patrons there. We will see them more towards the end of the night at park closing.