Let's say site A publishes an article. The owner of site B finds out about it right away, say through a push notification or email. He copies the article to his own website. Maybe even sets the publish date as yesterday.
Would Google know which one came first?
Even if Google could tell which one was first, would they care? If site B has better onsite or offsite SEO, would Google say, "You know what, site B stole it, but he's doing better with it, screw site A" ??