Sion ult does not collide with taliyah wall

I just played 2 games as jungle sion with my friend trying taliyah top. During both games, sions ult collided with taliyahs wall, but instead of colliding with it, sion would take a sharp turn and continue ulting down the length of the wall. The first time it happened it was a straight 90 degree turn that sent me barreling down the river instead of being in mid lane where i was heading. Second time was at a shallower angle, but i still turned and immediately started following the wall until i collided with regular terrain.

I was using the mecha zero skin in case that is relevant