I think it has some weight to it. For one he had alot of something called, "Human Emotion" he was sad that he got fired from his job so he wanted to get back at Bandai Namco by leaking the information to the internet. Not many leaks have emotion like this and usually sound like an advertisement, an example of this being the Smash World rumor, and they end up being fake most of the time. Another thing was that he did say that he respected Sakurai as a colleague, and said things that were totally realistic, such as him being stressed and having a hard time. He also stressed about how Sakurai was sad about King K. Rool and felt he let down the fans, which is also realistic. Another thing I found was about the region decided characters, I looked at the three versions of the ballot and noted they all had at least one difference, the American is anonymous, the European one isn't, and while the Japanese one is almost the same as the European one, the submissions for that one are recorded in full Japanese. Also this does correlate with the Shovel Knight rumor and Sakurai's reasons on including him. There is no other reason Sakurai would ever include Shovel Knight unless it was fanservice. He even mentioned how Sakurai broke his own code: Iconic third party characters that have contributed to something. These are all of the things I could find for the time being, if I can find anymore than I will post them.
