I was talking about NEXUS pre-clearance kiosks in Canadian airports. These do not accept Passports.

Specifically, let's say you fly Toronto-Pearson to New York-La Guardia. There is no customs in the US at this airport, so the US pre-clears Customs and Immigration in Canada, prior to departure. NEXUS members --- not GE however --- are eligible to use the pre-clearance kiosks instead of waiting in the line. In this case, since those kiosks do not accept passports, NEXUS members would be able to enter the US without a passport book.

GE members would need a passport book and can use the GE kiosks where they are available.