this might actually be the intended behaviour, since throwing the snowball is a seperate event, so if the snowball lands before the cooldown of the sensor is over, it detects the throw - from the player
An additional experiment revealed that if only one wool is used on the side from which the pilot comes, the sensor triggers later than expected, after the pilot already passed it.
Gabriel Jonas Thimm
this might actually be the intended behaviour, since throwing the snowball is a seperate event, so if the snowball lands before the cooldown of the sensor is over, it detects the throw - from the player