See this CBC Marketplace piece on travel health insurance.
Basically, from what I recall, those medical forms are impossible to fill out correctly and they are used to deny claims.
They make you fill out medical forms that are written by lawyers and for lawyers. Any minor mistake on the form is grounds for denial for any claim. So if you forgot you stubbed your toe 11 months ago, your aneurysm isn't covered. For one man interviewed they used unintentionally undisclosed GI bleeding to deny his claim for a heart attack. Even though his GI bleeding had nothing to do with his heart attack.
The form is impossible to fill out 100% correctly 100% of the time. The issues are:
-Patients, especially the elderly, a unaware or forget some things in their medical file, or the doctor explains things a different way than the form asks.
-You have to read the fine print of all of the definitions because they have "gotcha" clauses, such as the definition of "cardiac treatment" including diagnostic tests that didn't result in any diagnosis.
-Travel agents/salespeople give incorrect information to people who have questions about the form, even though they aren't authorized to give any information or assistance.
They suggest contacting your doctor if you have questions filling out the form but even if you were a doctor with full access to the patient's medical file, the doctor might still get the "legalese" wrong.
In Canada I've had zero problem making claims against health, dental, car, and home insurance. But pet insurance dragged their feet every step of the way on a very obviously valid claim. Definitely have no evidence but my first Avenue of thought is that pet insurance is probably less regulated.