I think it's treated as a comeback because it's the first time since last year that she is now back to being on magazines and TV performances, so while musically she never REALLY left, publicly she did, since her last TV live was in December.
And it's almost been a year since a proper single release accompanied with public appearances (TV Lives, magazines).
So public appearance wise, which I think it just as important in Japan, I would say it is a comeback, personally. We haven't seen her since December D: Which is why I am excited to see her TV Lives this weekend!
