I'm not sure if this is new or not. A large sliding object can affect a sensor if B is standing 4 squares away or closer. A small slider only has the effect if B is standing next to it.
I've played Resultant a few times, and yet I'm still mystified by sensors. I'll take a look at the Need Not To Know map and see if that helps me understand things better.
I'm also still confused about the sensor. There are still many mysteries that I do not know. For example when creating NNTK levels. where the ball (including the draggable/inactive motor) turns out to be a trigger at a certain position. Why did I previously say ball is not a trigger? because the ball cannot activate the sensor without a slider/robot/active motor.
Wow! The final design seems a lot simpler than some of your earlier attempts. It's cool that you finally figured it out.
Does the sensor require at least 4 components? Does the sensor work every multiple of 4? I don't know, currently still in the research stage.