Open Graph Metadata versus IndieWeb Microformats
Open Graph (OG) metadata is exactly that - metadata. It doesn't necessarily appear in the post itself, just in the meta tags.
For example, the open graph image, used to display when you post on Facebook, etc, can be any image, even if your article itself has no images.
IndieWeb metadata, on the other hand, is embedded in the post, which can be problem. You're really just tagging existing data in your post, not adding metadata after the fact. The "featured" image (an IndieWeb concept) is denoted as such via a CSS class and it should appear in your post, unless you hide it with more CSS, which can certainly be done but feels weird. This happens sometimes when you try to embed h-cards. I've sometimes hidden the HTML.
The Blurb
You can embed image and description data into the metadata of the post and arrange for it to appear as the OG or Twitter attributes. This allows your post to unfurl cleanly.
But syndication is a different problem. This is a copy - for some definition of "copy" - of your post. In the case of a small note, this is easy to do; just copy over the contents. But in the case of an article what do you use?
You could re-use the description, but this is likely to already be seen in the URL post you're sharing; Twitter and Facebook do their own unfurling here which will reveal it in the shared post.
So, ideally, you need another piece of content to act as the "contents" of the copy. This is the "blurb" in my website. You could also call it a "summary" or whatever. The point is that it is likely to be different from the description.