Redstone powering pistons through air

Hi,

I've found that pistons are being powered despite being 1 empty air block away, but only if they are attached to a piston is being powered, and has redstone 2 blocks above.

Removing the redstone signal doesn't work and requires a block update to one of the pistons to have them retract.

I get similar concepts have been used for BUD switches, but I didn't think it expanded across multiples.

If I remove a piston from the middle for example, the issue then doesn't affect the other half that aren't connected.

I had a quick scour through the bug list but couldn't see one related so apologies if it's already been raised.