That would be very unusual. Do you have reference to any real patient in that condition?
It's not uncommon after a severe head injury such as in a vehicle crash. Some of these patients, if kept on a ventilator and other support, may not meet the technical definition of brain death for a long time, and quite possibly not until organs have deteriorated to the point where they're unuseable for transplant. But their brain injuries may be so severe that there's no realistic chance of ever regaining awareness. If they also have physical injuries that would kill them soon anyway, and likely require them to be kept in a medically induced coma or heavily sedated in the meantime, what's the point? Most people would WANT to save other lives, if there was nothing else they could possibly accomplish in their short remaining life. Of course, people should be able to opt of being donors at all, but if you want your organs to go to others when you can no longer use them, the law shouldn't prevent that by imposing requirements that will often prevent the dying person from donating organs that will save others.