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The lower section disappeared at the same time that a message about "crawling suspended because robots.txt not accessible" appeared (several months ago). However, robots.txt was and is accessible and Google was and is fetching it, and was and is still also crawling the site!
They changed it a while ago such that if there are no errors, that particular error type doesn't show up.
I don't think I've ever seen a site with no 404 errors.