The source – twitter.com
It turns out that Google can remove those pages that were shown in the main news block from the main results.
This happens when a link from the main search results shows up in the first "Top News" slot. Since the news block usually appears above the main search results, Google leaves only the link in the "Main News" slot.
If, however, the news block does not appear in the top search results and there are organic results above it, there will be no deduplication, and Google will show the page there and there.