I find it strange indeed that only a day after the leak appears, there is the exact picture in Famitsu...
Like, it helps the leak at a good time.
Coincidence is strange, the picture used for the stage is exactly the same as the one in Famitsu, only a different angle...
So let's say it's fake :
-A person discovered this leak 20 days ago. He decided to focus his time on it.
-He first worked on the characters ; 12 to be exact. He decided to make four whole new renders while the rest is heavy photoshopped. Let's say he made it in five days, and instead of "he" there are many guys working on it.
-He/They then decided to make the roster CSS ; he thought doing things that "a fake leaker would never do" add some credibility to his/their case. Thus Yoshi in the middle of Mario characters, the triangle on Ganon's face, the thick line on Kirby, the three clones far from their series... Why would a fake leaker do it ? So you can question it and say only a dev team could do it.
-He (I'll stuck with "he", easier) then changed some background colors ; for example, Rosalina, because why not ?
-He also decided to change Olimar's icon by adding a blue pikmin, why not again ?
-He also decided to change some UI. Like the characters selected on bottom screen.
(notice the thick line one more time)
-He didn't put the Mii Fighters, well, bluff ?
-But it doesn't stop here ; he also changed Fox's background color to the exact one on the carboard of the game, instead of green it became cyan/blue.
-Now, he decided to make some more pictures ; first, one with the customization. OK, took at most 3 hours if he is slow.
-Then comes the SSS ; he decided to put a Xenoblade stage and an earthbound/RH one. We ar enot even sure, and thinks "screw that, only retro stage for DK and some other series". Didn't even put the final destination forms.
-He also had to change his SSS, since he got FAMITSU earlier with a new screen ; that would add credibility. He somehow lives in Japan. Brinstar was also added since revealed a day earlier.
-Took the risk to show Shulk and Dr. Mario in bigger renders, easier for us to find where they are photoshopped from.
-And, to come back to the CSS, removed all the names because he can.
Possible, possible...