Caught the tail end of a similar announcement the other weekend ATL-LGA, didn't catch the justification. If they're that concerned with people congregating in the aisle near the lavs, then they should probably come up with a better solution to the issue of people potentially cutting in line to use it. If I had to go that badly, I wouldn't be naive enough to think someone wouldn't cut in front of me if I remained in my seat as instructed.