Coincidentally we just had a very similar conversation over Thanksgiving. My son and his same aged (same college) cousin were talking about their apartments, grocery shopping, etc. They got around to talking about Costco shopping and my nephew said that his roommate’s parents take them to Costco every time they come to town and load them up. My MIL inserted herself and announced that included stocking the refrigerator with beer and that her son did not approve and would not be doing that (he was sitting right there but she felt the need to speak for him). My nephew shook his head and said “I don’t care if dad does it because my roommate’s parents keep me well supplied”.
This, in my opinion, is a case of overstepping by the roommates parents and they are opening themselves up to a liability issue. Knowing my BIL it could be a significant liability issue as I am sure he would look to cash in on a payday should anything ever happen. On the other hand my son sat there and didn’t say a word. I know he drinks, he knows I know he drinks I just don’t ask how he gets it and he doesn’t share those details. Over the summer he asked for a ride for him and his friend that was visiting to another friend’s house. It struck me as odd at first, why he wouldn’t just drive himself until I realized he was being responsible, was going to be drinking, and wasn’t going to drive. It was 4th of July so Uber would have been difficult and surge pricing so I was his next best option. Sometimes being responsible while doing something “wrong” is the best we can hope for during the college years.