TV-Nihon

I disagree with take calling people who say season zero rather then the Toei version ignorant. It's a fan term that makes sense, it might not completely fit in to the duel monsters anime but it's more or less an adaptation of the early chapters of Yugioh. Unless you're a fan of the manga it's the closest you can get to seeing the story from the start so you might as well enjoy it and consider it canon. It's about entertainment, over thinking if it is canon or not is a bit silly.

Everyone who's cool calls it season negative one anyway.

You say it makes sense, but you don't give a reason. Good job!

The first part of Duel Monsters is essentially the same as the end of the Toei version. It's not in the same canon at all.

Call it what you want in other places, but if you call it season zero here, I'm going to correct you for being wrong