Again, there are degrees of and variations in the degree of damage sustained, or of impairment resulting from similar damage. It’s likely one reason why MRIs are not acceptable as evidence of brain function and require great skill to interpret. Sometimes the visible damage doesn’t match the patient (I think there was a lady a couple of threads ago who’s poor father was in this position)
You can see how there are degrees in brain health, yes? How some people are good at maths (I’m hopeless!!) or good drivers or trip over their own feet? Well impairment is no different. It’s highly varied. And it’s one reason I don’t like the the term ‘brain dead’. It’s deeply unhelpful (as well as quite insulting). It’s never, never that simple.
Please give the medical profession the respect they have earned through blood, sweat and tears over their decades of training and experience. You simply can’t waltz in as a layman and say ‘case A is just like case Y’ without even having the test results, let alone the expertise to interpret them.