Redstone dust does not update to powered texture when it's powered by 1 tick pulse generator through pistons as shown in the video (direction of build doesn't matter). The redstone is actually powered and can be used but it just doesn't update to powered state as a texture during the time that it should. It does update in texture via observers though.

I'm not sure from what version this occurs from but i didn't experience this in the past and it isn't due to the world.