Actually not true. There is absolutely no scientific basis for any of this. I work with brains as a profession, and I especially am interested in the best possible preservation of the tissue so that I can report on it. It just doesn't work that way. There are incredible numbers of issues that are being taken lightly here.
Tissues have differential perfusion ability by different perfusing agents.
Different parts of the brain perfuse better than others because of the lack of fibers. However, many critical areas of the brain are perfused by blood vessels that pass through white matter and this are difficult to perfuse. An example is the substantia nigra. And we know what happens when we lose the dopaminergic neurons in the substantia nigra pars compacta. Sometimes they come out fine, other times, not so well.