Weirdly it's the ROB stage and bowling mode to me that make it seem realistic. Everything else seems... too Smashboards speculation too be true.
Picks like Karate Joe aren't really big Smash speculation elements. And we don't actually exist in a bubble. Stuff that's popular here is popular all around. You see the same kind of speculation all OVER the internet. And if this game is really *for the fans*, I expect a few of the picks to be more familiar.
That said, the leak is definitely one of the more interesting. Obviously, a lot of it could be coincidence. (e.g. "We haven't seen Pirate Ship yet so hey, a Gangplank stage is a logical replacement especially if K. Rool." (Though I could actually buy this. Zelda already has, what, every stage it's ever had +1 and Pirate Ship is still missing? Meanwhile, DK has 2+1 arcade mess?)
No Pokemon newcomer/no Elma also stand out as interesting.
Bowling mode sounds cool, but does anyone remember "The Tower of Smash?"
Honestly, between K. Rool and Paper Mario and Simon I'd be almost completely satisfied. Only slightly disappointing thing is the Echo choices, or lack of a Dark Samus but I'm not going to complain about that. We literally got Ridley.