It seems like Target UI could have benefitted a lot from a way to input the expected minimum sample size during activity setup. In that case, the Confidence reading could become conditional: it would only show after reaching the sample size, or it could show with some badge indicating that it's not ...

This was released in December 2019: https://docs.adobe.com/content/help/en/campaign-learn/campaign-classic-tutorials/sending-messages/email-channel/defining-interactive-email-content-with-amp.html

It can, as of Dec 2019: https://docs.adobe.com/content/help/en/campaign-learn/campaign-classic-tutorials/sending-messages/email-channel/defining-interactive-email-content-with-amp.html