That's not the theory
The theory isn't that Harada went to Sakurai and said to make sure these characters don't get in, the theory is that Harada knew of what characters were being added to the FP2 line up, and only listed characters he knew were not Playable, or even perhaps making a appearance in Smash
There were other Twitter accounts (like an Heihachi one) that were involved in the scandal, but Harada didn't list them, only those 6. Even if this incident was before Harada got big promotion at Namco, Harada was still in big spot in Namco, the team that's lending their hand at Sora.LTD for Smash development, and Sakurai and Harada have talked before, like about the prospect of adding Rollback. It's a real possibility that Harada might be more in the know about what's going on in Smash development.
It's very speculative though, and I don't know if it's the most concrete. I will say at this point it has been coincidentally lining up since none of the characters listed actually have showed up at all. Take of it as you will
Also to add into the Sora Train, apparently Harada actually unblocked the Sora twitter account sometime in June of this year...very shortly before that 4chan post showed up. It might also be the only account that was unblocked by Harada
There was a problem fetching the tweet
Due to that September post, that 4chan post is shady though. In any case though I'm liking the story that's going on regarding Sora. Stuff like KH Music playing in stores, the revelation that Harada unblocked Sora account, and the Disney game getting attention in the Direct, it's very interesting, even if it doesn't lead to much in the long run