The link is to a blog by someone posting their impression of what Dr. Goldhamer supposedly said. Which starts with "intuitively", i.e. he lacks knowledge.
The quote from Fuhrman's book tells me that he does not know what he is talking about either. He obviously does not fast himself. Nor reads what Russians discovered long ago.
Again, what "feels" intuitively right, ain't always so. Exercise is absolutely essential during a fast. Not hard-core workouts, but at about half of usual intensity.