I mean "at the top of the page rendered by a rendering engine".
I completely agree with you; Google does not have the technology to render billions of pages and to determine the position of the links.
The actual "random surfer" model guarantees equal probability to the page link's clicks. This is because there's no technology capable of determining whichever link has more probability to receive more clicks than another until now.
Whenever this kind of technology will be created, it will be useful, because it will generate more accurate results of which pages receive the most hits.