Observer sends out two redstone pulses when a piston head retracts in front of it

It seems to work correctly with a sticky piston and block. If the observer detects an empty piston is redstone dust, when in a chain especially, the result is a pulsing output. With sticky pistons and blocks the chain can be world height and you still just get one pulse output.

Confirmed on 1.0.9 / iOS and attached a very trivial test world.

Also note that when it observes a block pushed by a piston, it also emits pulses twice.

Win 10 - 1.1.4
any piston, sticky or normal, moving the piston head in front of the observer:
extending -> observer fires once
retraction -> observer fires twice

sticky piston with block moving in front of the observer
extending -> observer fires twice
retraction -> observer fires once

Fixed for 1.2.0.2 (referring to pistons only, not pushing a block)