An agent filling a form matches your labels to what it was asked to enter. An unlabelled field is one it must guess at - and a wrong guess in a checkout is worse than a refusal.
Impact is importance multiplied by the confidence tier’s weight — SPECIFICATION 1.0, RESEARCH 0.7, EMERGING 0.3, EXPERIMENTAL 0.1. Two rules backed by the same class of evidence therefore always carry the same weight, which is what makes the score reproducible rather than hand-tuned.