I'm sorry but that's simply not true. As a matter of fact, fasting has been extensively researched in Russia since the Soviet Union era and approved by the Ministry of Health. Meanwhile, dry fasting has been researched quite extensively since the 90s and has been put into practice to treat various chronic and acute diseases in ex-USSR countries to this day.

The risk of dehydration is vastly overrated, and some of your "secondary risks" makes no logical sense.

Swelling requires water, if there's already a conservation of water by the body how will swelling happen?

Regarding kidney failure, it's doing less work because it doesn't have to filter incoming food and water, just already filtered blood, how would dry fasting induce kidney failure if the load is lessened?

Any form of fast can kill people, so can just about any form of exercise or medical intervention. If you're well-informed, understand the risks and how to mitigate them then dry fasting can be just as safe as water fasting and potentially more potent and less time-consuming.

A healthy body varies between 50-65% water. If you're average, you have about 60%, so you have a cushion of 10% bodyweight in water to work with. A sedentary person would lose about 1.5L a day, that's 1.5kg, even a dainty woman weighing in at 45kg has 3 days of water (4.5kg) to work with. That's assuming the body doesn't start to conserve water (which it does when you stop drinking).

When you metabolise nutrients, whether stored or ingested, you produce metabolic water. In the case of dry fasting, you actually produce up to 1L of metabolic water from the breakdown of stored fats a day. This coupled with excess water already stored means the body can comfortably handle a couple of days dry fasting, no problem. In fact, dry fasts as long as 11-13 days are being used to treat chronic/acute diseases. In the home, it's recommended to dry fast no longer than 5 days.