Jar

@Galaxy_2Alex It's the next day, and I replaced the piston in the exact place and it was still powered. After, I tore out all of the redstone surrounding it and it was still powered. Then I updated the piston, and it retracted. Thus it was BUD powered somehow. Still, it should not have been powered as there were no blocks in a 3x3 radius around the piston.

EDIT: I replaced a redstone line that was above the piston. The piston then repowered. This is certainly a bug, as there should be no quasi-connectivity between these blocks, as there is a full gap of air between the block and the piston.

I tested with multiple pistons in two different worlds and the bug is repeatable.

I then tested it in 1.15.2 and still happens. There's no way this is intended, right? It doesn't make any sense based on the rules of the game. Diagonal power exists, but this is something entirely different.

It also happens in 1.12.2, which means it must be intentional.

EDIT: I conferred with a redstone discord, and it turns out to be intentional Quasi-connectivity. Thank you.

@Galaxy_2Alex If you look in the picture, there is no possibility for quasi-connectivity. I made sure that no red stone was powered or even near the piston.