Is it true that aerobic exercise is fatal for people with exhausted adrenals/chronic fatigue? can post-exertion malaise progress to post-exertion death? and what is the mechanism of fatality in that situation?

Adrenal insufficienc: People with adrenal insufficiency do have chronic fatigue and very easy fatiguability with exercise, but death from exercising is not a consideration as their body would prevent them from exercising to that point. It is true that serious medical events like infections, heart attacks, bleeding ulcer, etc or major surgery can cause dire consequences,however as they lack adequate adrenaline secretion

Adrenal crisis: Exhaustion or fatigue of adrenals is not well characterized as a medical disorder. Adrenal insufficiency is a serious condition that can lead to adrenal crisis when stressors such as infection or even extremes of exercise increase the need for cortisol. Adrenal crisis leads to dehydration, low blood pressure, low blood sugar, and high potassium. Death occurs after cardiovascular collapse.