The one theory about the immune system over compensating falls in line with the theories that it's a form of HIV ie manufactured. Also it could hang out in lungs which falls in line it's closer to high altitude sickness than a tradition respiratory disease that leads to pneumonia.
But I've known people who had mini strokes in their 40s but they also drank like a fish and were doing both body building and anti-inflammtory steroids through out their entire adult life. They were a non smoker but did the recreational pot, cocaine etc. Did a lot of sports and energy drinks. Point I think there's more to these patient's history they even they are telling the doctors. Know too many who tell the docs what they want to hear only. That being said this covid seems very versatile to say the least.