There's no way that thought process wasn't going on as soon as they started judging the entries. Because it's not like what the "casting couch" can represent is an obscure thing only known to fanatics, people know about it from the news, TV series, movies, etc.
So I would bet at least some, if not all, of the judges knew exactly what it represented, but they were all there going, "Well, I'm not going to be the one to say it..." because sure, they might say, "...because I saw it on the news," but you know they're thinking, "people will assume I know it from porn even if I say that." They might have even been scoring it higher to show just how very much they didn't know what it represented.
Probably one of them then came up with the idea of going, "You'll all be shocked to hear this, but a fact, that I definitely did not know before, has been brought to my attention: this is a pornography set! I know! We're all completely shocked, aren't we?"