Under the "AWS Anomaly" and "Azure Anomaly" resources types you can filter cost impact blocks by account or subscription. The filter offers both the option to include or exclude accounts/subscriptions currently but if you make use of the exclude option you will find that the policy won't fire currently.
This is due to a platform limitation for the two resource types mentioned above, you can workaround this by providing the inverse filter via the include option however.
To workaround the issue please take these steps: