The purpose described in the link is subsidiary to the actual purpose, which is as follows, according to the Reciprocal System of theory. Biological organisms are part spatial (body) and part temporal (brain). The spatial aspect comes from the material sector of the universe; the temporal aspect comes from the cosmic sector. In the material sector, the atoms oppose the space progression. In the cosmic sector, the cosmic atoms oppose the time progression. Sleep is necessary in order to resynchronize the material and cosmic aspects of a biological organism, otherwise the two aspects would separate. Sleep disconnects the two aspects so that they can become, once again, synchronized.
Study the Reciprocal System and prove it for yourself. http://transpower.wordpress.com