You are confused about the nature of the BUD.
Here, we have been speaking about the piston BUD all along.
- How do they work? You first need to power a block either 2 blocks straight above, or one block in upward diagonal. Like so:
Orange is the primary input. Green is the piston we want to activate through a BUD. We'll call him Bill.
But that remote powering isn't enough, you need to Update the piston for quasiconnectivity to operate.
- Anything will work as an update!!! Any change close to the piston will update it.
Be it lamps:
Or other pistons/block being pushed:
Or fence gates & gold rails...
Or a change of setting in an not even powered repeater..:
Input ON. Bill doesn't move:
Put repeater from 1 to 2: Bill updates an gets powered.
Input OFF. Bill stays powered. Damn!
Repeater 3 > 4. Bill finally notices that the input was OFF all this time and retracts.
Bonus: Both pistons are BUDed here. Left one is updated by the lamp. Right one is then updated by the left one.
See now? You can use anything to update the piston, growing vegetables, water, etc... If lamps are not able to update pistons in the futur, pistons won't as well, or anything else actually.