I am clearly way out of the loop when it comes to cultural analysis. I never even heard of Wall of Sound or Phil Spector, but some of the songs were familiar, and there are some lovely ones there. I guess I took backup sounds for granted because of their presence in jazz. They were not a wall, in most cases, however, but more like punctuation and response to some soloist; but maybe that's what the chorus provides is that response; or sometimes takes the lead.
One can find drumming walls in bebop, where the drummer is constantly active with some soloists. A number like Basie's Blee-Blop Blues (any version) is sometimes a wall of sound of a different kind, with sax and trumpet soloists threading through the band's backup. But I am probably misapplying the specific innovation of Spector in noting parallels elsewhere like this. Wall of Sound to me comes across as a specific kind of call-response. It's different from simultaneous interweaving and shifting lines in New Orleans jazz, which presents a different kind of wall of sound. In your definition, the wall has a backup choir.
The jazz sure did change as you note when the soul music changed.