I'm not concerned about the learned percentage or moisture levels. Since all 4 of the zones are the same terrain, soil, slope (St. Augustine grass), is using a sensor on 3 areas beneficial at all? Wouldn't the controller still send the data and water scheduling by itself?

Based on your reply, it seems like the Sprite alone isn't that accurate. You could advertise "Buy our Sprite but it only works best if you add the Whisperer. The Sprite alone in smart mode will not produce the best wagering schedule even though we've tired it to a weather station to get accurate rainfall, temperature and sunlight that's not enough. If you want your grass and plants to look their best, then you must purchase a sensor which only works for 3 zones. Although it may be weird that the smallest Sprite we sell is a 4 zone, but this will force you to buy an additional sensor! We get more money!" That's the image you portray so you might want to reconsider using a accuracy disclaimer on using the Sprite alone that it is not a "smart" without a sensor connected to it. And the 4 zone Sprite should specifically state that you must buy 2 sensors in order to get the best watering. Otherwise, the lower price than your competitors appearance is not true at all because you actually have to pay 109 for the Sprite and another 180 for the 2 needed sensor which makes your product close to 300 bucks to perform at peak levels. You are deceiving the public and they need to know. And why would you only sell a sensor that covers only 3 zones? Makes no sense.