Vines will Not grow or be placed on the back of stairs

I watched a video where someone was trying to place a vine to the back of a stair (not the bottom of the stair), and he could not do it. I tested it out on my IPad and found the same issue. I do not know if this is a bug or not, but I believe it was possible in older versions of the game. https://youtu.be/erkAxfQk4RM.