This is the default template with a featured image
Look carefully and you’ll see the featured image is centered on the dividing line between the header section and the body content section of the page.
This is easier to see in the image below…
On small mobile screens the featured image will span the full width of the screen.
You are reading a PAGE not a post
Because this is a page it does not have the excerpt option. In twenty twenty theme, POST excerpts display immediately below the post title.
I’ve made an example of a blog POST with an excerpt and a featured image.