Why make the distinction? My premise is that increases in physical activity tends to increase appetite. Doesn’t matter whether it is “volitional exercise” or NEAT. How are the calories burned standing at a desk (NEAT) different from the calories burned jogging (exercise)?
Heart activity is a major contributor to metabolism. If resting heart rate (RHR) declines while all else remains equal, then resting metabolism also declines.
Your heart is working harder at rest in low oxygen than at high oxygen. That means it is using up more calories and increasing metabolism. From (coincidentally) Banister Nutrition:
In the mountains, our very remarkable bodies can make several adaptations over weeks or months to make the most of the limited available oxygen. Your breathing rate speeds up to compensate, working the diaphragm muscles harder. Your body makes more red blood cells to carry oxygen, and those blood cells become more efficient at delivering the oxygen to your tissues. Simultaneously, your cells’ mitochondria (energy-producing furnaces) multiply to take in as much oxygen as possible. Changes your body goes through to adapt to the higher altitude can lead to a slight increase in basal metabolic rate (BMR), the amount of energy needed to keep your body running smoothly. With time the BMR lowers but does not return to baseline, so metabolism overall remains ‘slightly’ elevated at higher altitudes. Does Altitude Increase Calorie Burn? - Banister Nutrition, LLC | OKC Dietitian | Nutrition Specialists.
So your example attempting to show the opposite actually demonstrates the relationship between heart rate and metabolism…a small change in heart rate correlates with a small change in metabolism. The degree of this relationship varies enormously between individuals, but within an individual a change in RHR typically means a change in resting metabolism.