When statistics misinform you or are not aligned with your end goal they could divert your focus in ways that create no real impact or even steer you in the ‘wrong direction’. This is metrics that are harmful in action.
They could do this by hijacking you into making changes to your product or project for no real purpose or just to drive up these numbers, which have a chance of being for for vanity.
For example, webpage statistics can be a vanity metric when learning in the open