Not to pick on your post, since others have echoed the same sentiment, but my question again is why elevate "medical standards" above other standards that could similarly "put not only the diver at risk but everyone else in the group at risk"? RJP answered "all of those other things are fair game for discussion/questioning by buddies, instructors, dive ops, etc... but since they are not medical, they don't really belong on the medical form." But why is there a "Medical" form in the first place but not an "Other Things" form that could be just as pertinent? I suspect the only reason there is a Medical form and not an Other Things form is because medical is what immediately occurs to insurance companies to ask. If insurance companies really understood the universe of risk factors in dive accidents and were confident that gathering information related to those factors from divers would help their bottom lines, they would probably have different forms. But they pick on Medical because that's what they know.
Is there some underlying assumption that the diver does not have the same understanding of his medical conditions and medications that he might have about his other, non-medical risk factors/vulnerabilities? Why ask the diver to check off the box about high blood pressure and/or provide a note from his doctor, when the diver may have researched the heck out of it, consulted with physicians and pharmacist, and come to his own conclusion, as a rational adult, that his risk to himself and everyone else is low. Maybe the diver is himself a physician or pharmacists?--there's no box to check saying "I decline to disclose, but I have professional medication qualifications" that the dive op will trust. None of us dive with a ZERO risk to ourselves and others--there are always risk factors, just perhaps not medical ones. I just don't understand what makes medical risk factors so much weightier than other risk factors, other than that medical risks are something insurance companies are comfortable with. But with medical risks elevated to weightier status in the risk universe than they may deserve, the dive op won't let me dive if I check the box saying I have athlete's foot?
The dive op is unlikely to do anything with your medical information that is going to benefit you. The one possible exception is if you have a medical emergency, the dive op could dig up your form in hope it contains something useful to medical personnel. But how likely are you to have a medical emergency, how likely is the dive op to do that, and how useful is the scant information that is typically on those forms going to be? "Hypertension [box checked] controlled by [unspecified] medication [box checked]." I think the diver should be trusted to disclose or not disclose the information that he judges should be disclosed or not disclosed, whether it's medical information or any other potential risk factor.
As far as "lying" on a medical form by checking the "no" box rather than writing in "I decline to disclose," I guess we would be getting into questions of contract law, and that varies by jurisdiction around the world. But I can't imagine any situation in the US where there is some legal penalty for lying on a dive op medical form. As has been discussed many times before, lying on a medical form will only become relevant if the diver sues the dive op, and, I would imagine, if there is some connection between your injury and the lie. Only then could your "lie" be used against you. Otherwise, it's completely irrelevant.