I have recently encountered a weird piston behavior, where either a normal piston or a sticky one can be powered from the distance of two blocks. This is only possible by using redstone blocks (as far as I know).

Steps to reproduce:

• place down a sticky/normal piston facing any way,
• grab two redstone blocks and place them on top of the piston,
• destroy the middle block and that's it

Note: This would also work if your middle block wasn't a redstone block. I have recorded a video to make it easier for you to visualize. I have also tested it on 1.8 and 1.10 (I was able to reproduce it). And make sure your piston receives a block update.

Video: https://www.youtube.com/watch?v=tor1CBQcyb0&feature=youtu.be