I was expecting that is activated only the upper piston.

But activated and the lower piston.

Steps to Reproduce:
1. You need to put two piston(one above the other), so that they were directed towards.
2. Put any two of the block above the piston, and the second near the first.
3. Put redstone on the block above the piston.
4.On the second block to put a redstone torch.