The second route would redirect from the original url to the desired url so as to prevent duplicate URLs or to prevent errors in case the original URL is used anywhere.
The route you added above returns the page with the given slug when for example blog/2022/my-first-article is called.
The second route would listen to the standard $article->url() URL, e.g blog/my-first-article and redirect it to your target URL with the year.
Don’t really understand this question…
But the first route does not imply that the original URL is not accessible anymore. Or to put it differently: Without the second route that redirects to the target URL, the post would still be accessible under blog/my-first-article.
What does it not do > so a second route is required
But the first route does not imply that the original URL is not accessible anymore. Without the second route that redirects to the target URL, the post would still be accessible under blog/my-first-article