Interesting. I know this effect as a point of discussion regarding to EXTERNAL links. But within a site... and as the purpose of the anchor is to tell about the LINKED page....
As you say it may be dependant from certain factors, because every homepage links to a lot of subpages via the navi, but will not rank better than all pages.
Indeed this may be one of these factors. One that really would make sense.
Another could be the status of the linking page as hub.