I've never seen anything that suggest blood flow to the brain is reduced after a concussion. It non-blood oriented intracranial pressure goes up, blood will not flow as freely. Blood flows under pressure. Glymph flow does not have a pressurized mechanism. In the brain, there is a vast valve like network that directs blood flow to where it is needed more. After a concussion, this brain blood flow can get dysfunctional because this blood flow regulating system can malfunction. They do not know why this happens.

I wonder if the bigger problem is this need to flush the toxins out. Many cellular systems need a proper exchange and emptying before new nutrients can enter. Oxygen is a simple on. Oxygen and CO2 exchange places on blood cells so cells can function. When one gets CO (carbon monoxide) poisoning, the CO gets stuck on the hemoglobin so that oxygen cannot properly swap places with it.

If the glymph system is not functioning and allowing toxins to exit the cells, there is no room for the fresh nutrients to enter the cells. It's like a full elevator car. You cannot get on until someone gets off.

So, if one is not getting proper sleep with all the stages, there is no opportunity for the cells to drain off the toxins.