in the last snapshot of minecraft 1.12, when you try to make redstone descend in a stair full size side, you wont be abble to (despite if you turn it on from under, the redstone signal will climb). also, the levers and buttons cannot be placed on those full size sides (despite torches and r-torches can)

how to replicate:
redstone signal
-place a stair (upwards)
-place some redstone in the top of the stair and in the floor (in the full size side)
-place a lever (button, r-torch, etc) in the top and turn it on (the redstone signal wont descend)
-try the same activating it from the floor (the redstone WILL climb)

lever/button
-place a stair
-try to place a button or a lever in the full size side (you wont be abble to)
-try doing the same with torches/r-torches (you WILL be able to)

video evidence:
https://youtu.be/5Hxqx-p6CW0