Piston powered permenantly

When putting a piston down diagonally then putting a block of something like Iron above it then a redstone block above the iron block. the piston is not powered which is automatically strange behavior.

furthermore, when you get rid of the iron block the piston becomes powered permanently. unless red stone block is removed and then a block update is applied to the piston.

When all adjacent blocks are removed. behavior seems the same as listed above.