Anything silly would be ignoring medical advice in something very serious as cvd risk, believe what you want but would be very surprised if no insurance company wouldn't use it as a get out clause, or very least reduce payout on death.
Personally, I think lung cancer, COPD, cirrhosis of the liver and obesity are also potential killers. Long term lung cancer survival rates aren't good, even if it is detected early.
Contract law is contract law. The contract is made on paying the first premium, accepting the terms offered offered, based on declarations made and reports sought prior to writing the terms of the contract.
I worked in the financial services world for many years, including actuarial and underwriting. I have insight into how these things are done.
The harsh reality of life is that few life assurance contracts actually pay out death benefits, because some are fixed term and just expire at the end of the term, or customers stop paying their premiums (for whatever reason). Insurers are on a very decent bet with life cover, although of course they will take a proportion of big hits when people do die, whilst covered.
Of course, there are whole of life policies, but in the very vast majority of instances premiums need to be paid for the same whole of life. Some very old policies only collected premiums up to something like age 80, with cover remaining in place beyond that.