I had to read it several times to get it as well.
...regardless of what implied sections other headings may have created.
That is the part that answers the questions I believe. Yes, any
element that starts an explicit section is *not* a subsection of
nearest implicit sections. Also, any element
In 4.4.11, it says
Sectioning content elements are always considered subsections of
their nearest ancestor element of sectioning content, regardless of
what implied sections other headings may have created.
Does that line mean that a section element is *not* a subsection of
the nearest