So, I think it works correct from my testing. Zones are zones and have nothing to do with target watts. Your target watts of 55 watts is on the border of the zone, normally if someone wants to do zone based workouts they should have targets in the middle of the zone not on the edge. If they are on the edge then you will see red frequently. Zone training and power targets on the edge don’t make much sense. Power zones in themselves are a bit miss leading meaning the different in training between 55 and 56 is probably nothing yet it shows them as separate zones.
Three zones base on HR and ultimately lactate tests makes more sense. But most people expect the coggan power zones as those are most standard and very few people get lactate tests and even those tests are not perfect as your limits can change from day to day.
Not sure if my explanation helps.