I am not a Spectrum guy since I fly Futaba, but I think I may have your answer. I seem to recall with Spectrum, when you bind a receiver to a selected model on your transmitter, it will only answer when that model is selected. With Futaba, you can have many models bound to the transmitter, and if you turn all the planes on at the same time all the planes will answer to the transmitter. With Spectrum, if you turn on all the planes only the model selected will answer to the transmitter. This is done to keep the pilot from flying with the wrong model selected.
Scott