Keep in mind that these three/four characters might not specifically be rivals. They could just be recurring characters of another sort, and the characters you'd call "rivals"- those who get their own starters and who directly challenge the player- could be a couple of other characters. Or only one or two of these kids are the rivals, and the others are just friends.
The other thing he supposedly got wrong was Gogoat being the only ridable Pokemon, but with the way that was worded he might have only meant in Lumiose City. If I remember correctly, the Rhyhorn and the like are only ridable in later areas- He got this info by playtesting, right? Maybe he just didn't get that far before passing on the info.
Honestly, I don't think it's possible for this guy to have gotten so much right just by guessing, and there was no reason for him to deliberately give false info before it all blew out of proportion.