Redstone signal can be transerred by air

What actually happened was...:**

I place the redstone block that was higher for 2 blocks and wanted to place piston below and I wanted to use piston as secondary block, but the piston got extended. It works only if the redstone block above the piston.Also it stays extended when we brake the redstone block after placing.

Steps to Reproduce:

1. Put redstone block 
2. Place piston 1 block lower than redstone block (that actually works with sticky piston)
3. The piston is powered 

(that actually works with sticky piston)