Redstone blocks power piston diagonally downward

The Bug:

Any pistons will be powered diagonally downward by a Redstone block. However, pistons aren't powered diagonally upward or diagonally by a Redstone block. 

Steps to Reproduce:

1. Place a piston diagonally downward of a Redstone block (Like in the image).
2. It is powered !

Observed Behavior:

Any pistons will be powered diagonally downward by a Redstone block. 

Expected Behavior:

Pistons shouldn't be powered diagonally downward by a Redstone block.