I'm fairly certain the leak is incomplete. Especially since the leaker seems to have been going by memory (he made a few spelling errors with Pokemon names, though it was still close enough to be clearly legit). In that case, it makes sense that he relayed only the information that was interesting enough to stick in his head, like weakness to Poison and Steel and immunity to Dragon. He didn't mention any resistances, at all, which would be very strange.
Still, I believe that what we've been told so far is accurate. It's just not everything.
Socran's Razor: "Never attribute to massive stupidity by someone else, what could be explained by a tiny bit of stupidity on your own part."