Hydraulic torrent explexplicitly allows creatures of any size. Hydraulic push says nothing about size, just that you perform a bull-rush against the target, so it implicitly allows it. Just because hydraulic torrent explicitly says something does not mean it would not be allowed anywhere else.
Think about is, would a halfling have a smaller hydraulic push than a human? That's racist man ;-)
I do not think that imbalanced. The CMD mechanics handle this just fine. Large creatures are quite hard to bull-rush anyway. So they should be fine.
I couldn't find rules about bull-rush and flying and the spells don't say anything about tszthe size of the water spout/tsunami, so... Common sense would say push is smaller than torrent so yeah, torrent could count as a collision, push wouldn't.
But in PFS, expect table variations.