This makes sense to me for articles and the like. If the point of the page is information, it makes sense to me that the page should load content first. OTOH,

This makes sense to me for articles and the like. If the point of the page is information, it makes sense to me that the page should load content first. OTOH, twitter, slack, and package tracking are consistently changing. It makes more sense for something like that to load content via JS, since there's no guarantee the page looks the same between two loads