MDs give you incorrect information too. I had a GP for 5 years who, when I talked about my cataplexy - a well-documented condition that is directly related to my (at that time, undiagnosed) narcolepsy - he told me to go on birth control, then he changed my antidepressant meds, and then when those things didn’t help me, he said “try exercising more and lose some weight”. If he would had looked up the symptoms I was describing (like I eventually did), he would have probably recommend I see a sleep doctor, but instead, I lived with narcolepsy under his care for 5 years, almost getting fired for falling asleep at my job.
I know it’s not the same, as your brother had a life-threatening condition, but all this to say that MDs aren’t all outstanding professionals either.