Right now, there’s only the Kepler telescope data to work with. It’s one of the strongest candidates for an exomoon to date (most candidates fail quickly), but not so bulletproof that you’d stake your life on it. The scientists want to collect measurements from the Hubble telescope before they can make an authoritative statement one way or the other. This is probably an alien moon, but you never want to rule out the possibility of another object.
Of course, a bona fide exomoon wouldn’t be shocking. Ask anyone with a passing interest in space and they’ll probably argue that moons are common in other star systems, if just through sheer numbers. Rather, it could represent a big milestone in how humanity studies space. Where the focus so far ha been on spotting the largest objects, this suggests that astronomers might have some success looking for the minutiae of a system. And that’s more important than you think. Earth’s Moon increased the chances for life on its host planet (by stabilizing the rotation and shielding it from asteroids), so it’s conceivable that an exomoon might produce a similar effect.