I don't believe Google uses a parent/child type of categorization where the "parent" or higher directory carries more weight.
Now that I can agree with 100%. The page relationships are derived from linking structure, not URL structure. (Which is why I suggest that a flat site map page can be a detriment - it doesn't give life to the relationship structure).
Let's look at this a little more, too because there are things where directory/page naming methods do influence relationships:
www.domain.com/ezine/authors/bios/person.html
Let's say I changed it to:
www.domain.com/ezine/authors/xyz/person.html
Even though I didn't use the word "bios" anymore, every page in the XYZ directory is likely a biography. Once the spider gets to enough pages in that XYZ directory to see that "Biography" is the common "general theme" of each page and that "person.html" controls the specifics of what that biography contains, then when you add a new page, the spider knows some of what to expect from it.
Compounding this, your "person.html" pages most likely work from a common layout. The photo of the person is always "here", the person's name is always "there", and their birthday is always "down here", and the details of the biography are "right there".
So, now that Google knows that all the pages in this directory are bios, it also knows where on the page the "who's bio is it?" information is going to be. If that section of your site lists "Inventor's Biographies", then there is a decent change that your "hub" page (the page that lists all the people and links to the bios) will rank fairly well for "inventor birthdays" even if the word "birthday" isn't 'optimized' on the hub page (though it probably will need to appear once or twice). If you search for "Thomas Edison's Birthday" the specific page for Edison may rank pretty well - even though the word birthday only appears once on the page - why? Because you've shown a pattern of consistently providing birthdays of inventors on your pages. (I know that this type of thing has been happening for some time as my movie site - that came down late last year - used to have celebrity birthdays listed and I tended to rank very well for this type of search. There are similar type things going on in various other sites I oversee, too).
Consistent naming conventions and page layout all play a part in this and it's all tied together by the linking structure that echoes/mirrors your naming convention structure.
G.