I belive the dehydration to which he is referring is that of the bacterial organisms, not body cells. Most likely due to the high osmolarity of the honey, the semi-permeable membrane that makes up the bacterial cell wall allows water to leave the cell, thus dehydrating the bacteria.
One thing to keep in mind regarding raw honey is never to feed it to children less than 1-year old or anyone with an immuno-compromised condition, such as patients undergoing chemotherapy or other immuno-compromised diseases. Clostridium botulinum spores will remain dormant in raw honey can reactivate within the intestinal tract. Most adults with normal gut flora (bacteria) will prevent the clostridial organisms from colonizing the GI tract. Children less than 1 year of age likely do not have sufficient gut flora to prevent the colonization of the GI tract by the clostridial organisms and may develop botulism. The same can be true for immuno-compromised adults, who may succumb to becoming infected with Clostridium botulinum and develop botulism.
Pete