As shown in the below screenshots, when placing water on the backside of stairs, the water flows through to the other side of the stairs rather than where it's intended to be. This happens both in creative and survival modes with an individual stair placed and when it's connected to other stairs (i.e. making a well). However, when placing lava, it works as I'd expect it to.

I've searched for "Water, Stairs" and the closest ticket similar to this issue is closed as "Incomplete" (MCPE-55588). I haven't been able to find another ticket explaining what I'm experiencing.