Bug with block of redstone

I dont really now if this is a bug, or you did it to happen like this.
The problem is that if you put a sticky piston and a block of redstone together (in horizontal), and then
you activate the piston (with a redstone torch for example)the piston normally pull the block of redstone, and when you deactivate
the piston, it normally pull back the block of redstone
BUT
if you do that on vertical, if activate the piston, it pull up the block of redstone, but when deactivated, piston remains extended
i supose thats because of being powered by the block of redstone. I dont really know if that is a bug, or you did it to happen this way.

What I expected to happen was...:
When placed in vertical, a sticky piston and a block of redtone in top of it, and you activate and deactivate that piston, it should
extend and dis-extend, pulling block of redstone up and down

What actually happened was...:
What happen right now, is that piston extend normally, pulling the redstone block, but when unpowered, remains active, not going back
and pulling down the redstone block

Steps to Reproduce:
1. Place a sticky piston on the floor (the pulling side looking at sky)
2. Place a redstone block on top of it
3. Activate the piston with a redstone torch
4. Deactivate the piston destroying the torch

Im sorry if this was reported yet, I tried to find something alike in the search tool with no lucky. And sorry for bad language too, im Spanish

Cheers johnnialben