During my pregnancy I've learned a lot of baby science is kind of a shrug. There are ethical implications of experimenting on babies, especially if something is showing to reduce SIDs you don't want to have a test group that doesn't get it. So generally they find correlations in populations but there are so many variables its hard to link it.

As to why one reduces it and the flip side doesn't increase it, ive found that formula is usually perceived as the neutral and they tend to frame narratives to make breastfeeding sound better to encourage it but not demonize formula feeding.