No, collecting biometrics at registration is required by the legal framework they operate in (a.k.a as a "Registered Traveler" program [0]). However, they could

No, collecting biometrics at registration is required by the legal framework they operate in (a.k.a as a "Registered Traveler" program [0]). However, they could use other biometrics like fingerprints if they chose. [0] https://en.wikipedia.org/wiki/Registered_Traveler https://en.wikipedia.org/wiki/Registered_Traveler