Missed Blade Runner Opportunity

At one point Rachel (the replicant that Deckard hooks up with) asks Deckard if he’s ever taken the Voight-Kampff test (which determines whether someone is a replicant) himself. I’m surprised the story didn’t do more with this potential plot twist. Deckard’s character would have been more interesting had he wrestled with the suspicion that he too is a replicant.