Removing blood (a “therapeutic phlebotomy”) is healthy and necessary for specific medical conditions like iron overload (hemochromatosis) or too many red blood cells (polycyt hemia vera) to prevent organ damage.
But general bloodletting for wellness is not, and carries risks like infection or fainting.
This procedure does not appear to be a general blood letting - as in mere removal of some blood. There is no actual blood loss. What is removed is returned after passing through a filter and an oxygenation process.
That our blood stream can be carrying an excess of toxins that our internal blood filtering systems can be struggling to manage and not always doing a bang up job of is understood in medicine today ; and from it many different sorts of inflammation can be occurring, resulting in at best sub par health and at worst chronic ill health conditions.
The idea behind this blood treatment is to take a good degree of the blood filtering load off of the internal blood filtering organs, which not only externally achieves blood filtering but helps the internal blood filtering organs function better with a lighter load.
The toxins are to a large extent a result of a lot of the artificial things in our modern world, in our air, our water and our food. We - humans - do seem to generate more of then than does the natural world.
Yes, more primitive societies often have shorter life spans due to some major ailments that don’t get modern medical care. But they also have fewer of the modern chronic health conditions that plague many people for many years.