I'm developing a WP site with a blog. I want to show the blog posts by assigning "blog" as a parent category to all posts and using that category archive page to show the blog posts.
I would not use the standard "posts page" in WP.
Then I read this: (with Blog Page he refers to the "posts page".)
The Blog Page gives out several indicators to social sites and Search Engines that it's a Blog. First and foremost, it's called a Blog, it has a collection of Titles with URLs assigned to them and some Themes even include Microdata. It's paginated, and with HTML5 multiple Article HTML-tags also may be output. [...] In fact, WordPress requires a Blog page to be available.
EDIT: Quoted from this thread.
Why would search engines care with what method the page showing blog posts is built? The parent category archive page also is "a collection of Titles with URLs" etc. and would be almost 100% the same as a "posts page" AKA "blog page".