From own experience, I rather suspect that you have the right of it. Secondaries are never any fun, even if they come to a reasonable resolution in the end. I signed up for NEXUS in part to make the southward journeys less-stressful (even though I expected that there would still be line-ups), and to speed the northward journeys. I am not sure that GE offers that much functionality to non-immigrant Canadians, in the end. Having to have one's fingerprints retaken is a non-issue, as by this point I would expect that we've all aready got voluminous identifiers on file, on both sides of the border. On another side-issue altogether, on my most recent land-mode shopping trip down from Vancouver to Seattle, the northbound lineup was actually ten minutes longer for NEXUS than for non-NEXUS. Am still puzzling over that.