Use Lion's emoji to hack Google ads

> Any ad that contains a character from a predefined blacklist of special characters is automatically flagged for manual review and promptly denied by Google's approvals department.

I can understand the use of blacklist for flagging for manual review. But I don't understand why new, previously-unknown characters are allowed. If they were using whitelist for approved characters, certainly the emoji characters would have been stripped, replaced, or flagged for review.