My friend, that eassy was written in 1969.

Much of what your sighting wasn't cannon yet, and given the internet didn't exist, nor did the kind of nerd culture we have today, it's entirely reasonable for a writer at the time to not be expected to have encyclopedic knowledge of Superman canon. Insofar as there even was true canon given it was the twilight of the Silver Age, when "bonkers" was the name of the game.

Moreover, that eassy is pretty famous for being such a candid, deep dive into such a silly topic but bringing up something most people at the time hadn't considered. This was 1969, published in a mens magazine, by a sci-fi writer, that basically took on meme status. It's pretty obviously not meant to be taken seriously.