Actually, there is an interesting little tidbit about that post that gives it a little more weight as a leak, do take note of the topics title, and the very last comment
"Things I want for the third version of SM USUM"
"This totally isn't any sort of leaks and don't screen cap Let's wait for the game to be announced ;(
Don't those two things seem a little off? the title even lists the names of the games yeah? then why did he say "Lets wait for the game to be announced" how can he list the games he's talking about if they haven't been announced yet? the post was made March the 28th, have we known about these games that long already?
No, we haven't
We didn't get the announcement of these games until June the 6th, over two months later, yet he not only knew their names abbreviations, he also knew that Necrozma was going to get new forms, plural as well as new UB's
Doesn't that seem strange? :P