Well, "dangerous" for who? For a lot of people involved in "child abuse" – from medical professionals to child services to the police – a false positive carries basically no consequences: you report it, or follow up, or do whatever your task is, "to be sure", and that's it.
But a false negative can have a lot more consequences, including losing your job, lawsuits, becoming the centre of a media circus, becoming the target of an investigation yourself, etc. etc.
Also see: most Amber Alerts should not have been sent, and are just simple cases of runaways, miscommunications, or family drama. But the official "pushing the button" to send out an alert has the same incentives as above.
The incentives are pretty obvious.
Infants are routinely given vitamin K and vitamin D to prevent bleeding and to prevent bone development issues. Imagine if there was something else that could be given to prevent brain bleeds. That would save a lot of children.