No matter how low the fatality of a patient condition is, a professional doctor will never promise to save the patient's life or give assurance that the person would survive. All they would say is, we will try our best, meaning anything can happen

This was quite common when HIV testing first gained prominence around here. Many people fainted, some even died of on the spot, once they're told they're positive. So, medical personnels had to be creative about presenting results.

Honestly, withholding truths to protect potentially combustible situation is not a problem, but doing that to mislead or gain an advantage is mean. Funnily enough, most people do it.