Steps to Reproduce:

1. Place a stair
2. Place a corner stair
3. Place a wall/fence/iron bar/glass pane on both back sides of the corner stair

Observed Results:
The wall/fence/iron bar/glass pane only connects to one back side of the stair.

Expected Results:
The wall/fence/iron bar/glass pane should connect to both back sides of the stair.

Original Description:
While building with the new 1.16 wall mechanics, I discovered that all of the walls were connected to the backs of stair blocks except for one in the corner. After experimenting, I found that wall blocks attach to the back edge of a stair block only, which makes sense. However, when I placed another stair next to the first and made it a corner stair block, the wall on the updated/second back side of the stair did not connect—even after updating/replacing the disconnected wall.