It looks for the tactics that scams rely on, not for a specific known scam. A message can score low and still be a scam, and a legitimate message from a delivery firm can score high because it genuinely is urgent. So treat the score as a prompt to slow down, never as a verdict.

The single most reliable habit is also the simplest: do not use the contact details in the message. Look up the organisation yourself through a number or website you already trust, and contact them through that. Real banks, HMRC, the police and utility companies are all reachable that way, and none of them will mind you checking.