Generally medical websites do it in the UK, as a warning to sick people who Google their disease looking for advice and land on research papers or scary information for specialists

My first thought was a conversation with a med student friend about the tension between medical research transparency and public policy. For example, it's good to get vaccinated, but some small fraction of people do have lasting side effects, and vaccine skeptics blow it out of proportion to support their views. So, medical professionals may be tempted to downplay vaccine injury to support public vaccination. Of course, doing so just erodes trust further if people notice. Anyways, perhaps this website is afraid people will hurt themselves with ambiguous information.

It's probably underpinned by the same sort of "we're legally/contractually obligated to ask but we really don't care" type situation.