I don’t think so.

If they only relied on the sensor it would constantly turn on and off which is something I have never seen on that kind of faucets. I think there is always a delay before shutting down but sometimes that delay is set so low that it feels like you need to constantly activate the sensor.

Edit: clarification: What I meant is that if you just move once your hand in front of the sensor it should remain ON longer than just the time your hand was detected. I have never seen a sensor that literally activates only to the millisecond when something is moving. Even just to prevent false activation for half a second you kind of need a delay in there. If not you could have a 100ms activation that doesn’t even have the time to let the water out by opening the faucet and you create unnecessary wear on the valve system. My point being it never really makes sense in engineering to have a button or sensor direct output used. Usually you have mechanisms to prevent “bouncing” and so on. But I’m no plumber so it is just assumptions.