CSS properties that reached Baseline recently: supported everywhere, but not for long enough that un-updated installs all have them. Reported for awareness and excluded from scoring - adopting one is a decision, not a defect.
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.
Built at scan time by browser support data, not from our static registry. That engine evaluates its whole rule set in one pass, so this check cannot be run on its own — it runs as part of a scan.