Piston get activated when theres no redstone connect to it.

I placed down a piston. 1 blocks above the piston, i placed a stone block. (between them is 1 air block). On the stone block i placed a redstone and activate it with a lever(turned on) placed besides it. So, with an air block between the piston and stone block, piston wont get activated because there's no redstone connect to it.

But surprisingly, it activated when i do some block changes near the piston.

Steps to Reproduce:
1. Build a structure like this: A piston on the ground. 1 block above the piston place a stone block. (Left 1 block space (air) between them).
2. Place activated redstone on the stone block. (Activate it with restone torch, redstone block, lever...or things that provide redstone energy)
3. Do some block changes around the piston. (Put a block behind it, destroy a block behind it, replace it, or put a block on it.)