Its not, he has like a vest thing on in that art, an dhas a skirt type situation. And different hair and face and entiery. It isn't the same, also that doesn't prove your point, even if it was the same, because could suggest sakura's outfit is her alt.
So its not the same and it doesn't matter
It's not a vest, it's a piece of cloth/sash thing that goes over his shoulders, rises up behind his head and is tied in knots at the side of his waist. Which is what he wears in the game, except it's thinner and not as long there (presumably because this game doesn't do big, puffy, flowing clothing very well). The same is true for the "skirt". It looks like big, flowing pants, which have been toned down in the game.
Like I said, he has the same hair as his default model. Maybe because they figured making another style of big hair for Akuma wasn't worth when one was already perfectly usable, I don't know.
I don't think anyone said that it wouldn't be a DLC Outfit, the argument was against it being her main one
As I said, if she were to be added to the game, I expected it to be her default, though as Ryce pointed out, the original DLC characters were always intended to be DLC/playable whereas that isn't the case with Sakura. So I could see her having a different default outfit as a result.