Parental Controls for Mail does not present all emails to approver

Those of you who use Parental Controls to manage your children's use of email via Mail know that you can restrict emails they receive to ones sent by people on a whitelist, only. If someone not on the whitelist sends a message, it should be first sent to you for approval, after which it is let through to your child in Mail.

That's the theory. Putting this into practice I sent messages from my various email accounts to my son's email address. None of those that weren't on the whitelist got through--that's good. However, I received permission requests for only two of those messages. The one sent from my work account simply disappeared--that's bad.

Do any of you have a sense of how robust this part of Parental Controls is? I did file a bug report on this, by the way.