When sticky/regular pistons push redstone blocks, they don't retract upon being "turned off"!

What I expected to happen was the piston to retract just like normal!

What actually happened was, even when I flicked the lever back to "off", the piston stayed up just because it was pushing a redstone block.

Steps to Reproduce this bug:
1. Put a piston behind a redstone block
2. Use a switch to make the piston push the redstone block
3. Turn it off, it won't, just because it is pushing a redstone block