Any page with only an "About" section is hopefully a page that will be expanded. I generally won't put in an "About" if I can't see the need to ever expand a page to that point.
I almost want to put "links" in a separate tab or subpage... the links section can take up more than half a page, especially for an older article with a lot of filed links (e.g. George W. Bush), and that distracts from the content... but at the same time, it's nice to be able to see quickly that there's a lot of additional information available. Ideally (technical considerations aside), it might be nice to have a sort of "links summary" on the main article page -- "There are X references, Y news articles, and Z projects relating to this page." -- with a link to the "links" subpage, but there's some work to be done before that would be practical.
I also have a sort of OCD thing about parallelism -- if all the other h2 sections are one short word, "External Links" kind of sticks out awkwardly.
None of these are compelling reasons, but I'm also not seeing a compelling reason to do things differently. Further discussion welcome.
My general preference is that if it's sensibly possible to put all information on a single page, then do so. Every link you traverse is a usability barrier.
More generally: a link should provide access to additional but not immediately relevant information. A link to a page of links doesn't cross that threshold, unless it's some _tremendously_ long set. The general guidance at Wikipedia is that the external links list should be short, relevant, and primary. The references section should be as comprehensive as necessary. I don't know if there's a way to find a Wikipedia page with the most references but Wikipedia:Vivian Schiller has 36 references, totaling about 1/3 the page length. The Wikipedia:2011 Tōhoku earthquake and tsunami page runs 354 references and another 23 external references. They take up 23 of 48 screens on my monitor.
Not sure I buy the parallelism argument -- words are for communications, not (principally) psychological appeasement. Though I will smith writings to remove awkwardness myself frequently.
I do like the idea of a stats summary on a page. Links in, links out, references, edits, most recent edit, pageviews. Possibly others.
I tend to go the other way -- I find large blocks of text much more difficult to process, and prefer to have subtopics summarized with a link so I can see quickly which areas are covered, and can look at a given subtopic without being distracted by the others. But not everyone has my particular variant of ADD. An extension to automatically transclude subpages if the user chooses that as a preference might solve this dilemma, and is something I came up with awhile ago and found appealing.
I take your point about usability barriers, though, and I have at times wished for a "single page" feature wherein all appropriate subpages could be combined into one. There's an extension called "Book" (I think) which lets you create a collection of pages and pump them out as a single PDF; I'm not sure if it offers a single-page view of the collection, but that seems like something that wouldn't be difficult to do. It also shouldn't be difficult to create a "page-flattener" extension which adds a tab at the top ("flat" or "single page") which displays the current page plus all subpages as a single page.
Also, for what it's worth, I've made conscious (but largely undocumented) decisions not to go with Wikipedia's conventions in a number of areas. (Collecting news items that discuss a topic, rather than being primary sources on that topic, is one such area.)
Words are for communications, but conventions are sometimes helpful towards that end as well. If I keep to a convention that a "Links" section is for external links and a "Pages" section is for internal links, then I can communicate the same ideas as "external links" and "internal links" less ambiguously and with fewer words.
I'm still thinking about this, though -- not decided. Issuepedia has been largely on the back burner for the past couple of weeks. :-P