Not discussing normal everyday parts of life can only end badly in shame, confusion and recriminations.I don't know if it's a problem. I'm not sure in this case. However for me it's between "How would this shape their environment" vs "anything they see or learn doesn't matter because a gay dude knows he's gay automatically and a straight person knows they are, always".
As parents are often rubbish at duscussing anything sexual with their kids, especially "difficult" subjects school is the perfect place for such things.