No customs forms were being collected at SAN last summer when I arrived from LHR although the BA was giving out paper forms. SAN has undergone recent renovation and although there were GE kiosks there were no APC kiosks. At the time I was not a GE member so I was not sure how GE was being processed although there were kiosks which I assume were giving out printed declaration forms. As a non-GE member I simply collected my luggage, went to the officer, a few quick questions and I was done. It seemed like they were using some sort of facial recognition to verify identity.
This also made me think of the value of GE if non-GE passengers can get though without filling forms but GE member need to fill out forms on the kiosk, declare food etc.