Well, maybe it just looks similar, but actually functions differently. Kinda like how Inkbrushes work like Rollers (in that you swing them, then hold ZR to run with them on the ground to ink turf), but in practice are quite different (Inkbrushes are much faster than Rollers, but their swings are weaker, thus requiring a different playstyle, or at least it does for me).
And now that I've seen a Slosher in action (also, is the weapon calle a Slosher, or is that the weapon type? Or is it both, like with the Inkbrush? Does anyone know yet?), it looks nice, though weaker than I thought (though it might be stronger at close range). Definitely trying it out when it comes out.