It's difficult to prove that the "error" is authentic because the maple leaves can be removed with some solvents without any traces...much as the famous OSD on the 20$ note in the Birds serie (which was initially acknowledged as an error until it was discovered that the error could be faked).
If this note comes directly from a sealed brick, maybe (and a big maybe) it could be an authentic error, but if the note was found in circulation, the odds are higher that is a fake.. In any case, there is a doubt...