My understanding is that the falsetto(as well as the other altered vocal styles, such as that whispery bass, and that froggy voice) come to Black Gospel music by way of JuJu from the old African religions, where they occur in religious rituals when the singer is possessed by the spirit of a particular god--there are vestiges of this in white charismatic rituals as well, such as in "speaking in tongues", and I am pretty sure have heard falsetto singing in mixed charismatic services, but I think you're right--