Non-sectioning <nav> elements

Hi there!
I'm going to ask some information about an issue which has already been
exposed elsewhere by Reinier Kaper, unfortunately with limited discussion.
The question concerns <nav> element. The spec describes it as a "section
containing navigation links", and therefore <nav> is listed as sectioning
content. However this means 2 things, one of which is also implicitly
referred to in the prose (4.3.10.2 Sample outlines).
On one hand, take a page structured as follows:

[header with no heading elements]
[navigation]
[main with its own heading element]

This means that the page has no title on its own and it revolves around its
<main> element, whose title is the page's title too. Site navigation in
placed a <nav> element outside of it, which is semantically relevant, as
this navigation is not part of the main content. This forces the body to
have no title and the benefit of non-sectioning <main> (i.e. the fact that
it does not necessarily defines a subsection) is lost (although it can
still represent a top-level section), so that the outline is

[body] (untitled)
  +  [nav]
[main] (titled)

This can be extended to sectioning content elements whose heading is
preceded by a <nav> element.

On the other hand, having an only <nav> inside an <aside> element (which is
also semantically relevant, although the spec suggests to use <aside> for
grouping nav elements) forces a useless outline expansion
[body]
  +  [aside]
        + [nav]
This makes little sense, as the inner "section" is the only content of its
parent (apart from possible heading elements in order to avoid unpleasant
"untitled aside" - and there have to be 2 of them, as there would be an
equally unpleasant "untitled nav" otherwise).

On a purely logical point of view, <nav> seems to define a tool for the
page, a semantical grouping, like <main>, rather than a section. And like
<main>, it should be the author's choice to have a "navigation section" or
a "navigation side section" by putting <nav> inside <section> or <aside> as
necessary.
So are there any technical reasons why it is considered sectioning instead
of grouping, as it would be intuitive?
Thanks for all feedback.
Andrea

(this message is CCed to the original proposer)