Your sarcastic example really falls flat.
The source he claims stated that the six would be shown off at E3 barring impromptu change.
We literally got half of the listed characters, two of them being ones no one would have seriously expected (especially the Wii Fit Trainer). There is no coincidence there.
The corollary is that he got half of the predictions
wrong, and while almost nobody would have predicted Wii Fit Trainer and Villager together, out of a fanbase numbering in the tens of millions,
somebody certainly could have. Several posters here claimed to have expected something for Wii Fit following the reveal. Furthering this point is the fact that as far as we know the source did not say "Villager and Mega Man for sure, and the others subject to impromptu change", but rather just rattled off six characters.
Like I said, I think all three have good chances for inclusion, and that rumor may indeed eventually prove legitimate. We just shouldn't treat this rumor as a guarantee of their inclusion, that's all. The source was not verified, the source was not specific regarding the release timetable, and the source was wrong about 50% of the characters, which means that right now we need to treat it as fake until proven otherwise.
You're claiming one thing that has absolutely no credibility to back up.
Agreed. However, my point there is that saying "barring impromptu change" adds absolutely no validity to any leak, because it's the most basic defense for a fake leak you could find as there's no way to disprove it.
For my money, unless the source found out about the planned E3 reps a month or two out, which is certainly possible, last-minute impromptu changes in the planned announcements for that many reps at such a major conference seem very unlikely.