I think the purpose of the 'next' and 'previous' is to move to the next/previous page (i.e. file) and not another section in the same page. If you read a page till the end and then you press 'next' you probably want to go to the next page, not to next section that is in the middle of the page that you just read.
I agree that sometimes it looks weird though, especially in the index.
The only thing that IMHO could be "fixed" is limiting the number of sections in a page to 1, otherwise I'd just close this as "won't fix".