Biometric IDs are unique and beat the traditional paper-pen or card systems hands down. Cards can be swiped by proxies and attendance can be fudged. It is a common malpractice, often seen at plants within contract workers.
The thumb IDs are biometric too, but they have failed to meet the hundred percent benchmark. Women using Indian Mehndi on hands feel frustrated when their thumbs don’t get identified at office machines. Similarly, plant workers who work on oily machines cannot walk past a thumb-based system easily. Besides, it is not touchless, and it takes multiple attempts for one correct match.
Face recognition is truly the only unique identifier, doing its job in few seconds. It cannot be proxies or scope for manual overrides.