Explanation
When a user creates and resumes a new automation rule, the rule will continuously look for prospects who match the criteria (B) and evaluate their entire prospect database for matches. These are the characteristics of automation rules in Account Engagement, which are different from segmentation rules that run only once.
The rule will not run once and must be re-run for prospects to match again (A), nor will it unmatch prospects that no longer match the criteria (D). Unmatching prospects is only possible with dynamic lists, not automation rules. References: Using Account Engagement Automation Rules vs. Salesforce Flows