For many sites, this probably is a premature optimization. But for sites that live off of click-through, like news/media, getting the text on screen is critical. Bounce rate starts to go up and ad revenue drops as soon as page loads are less than "immediate", which is about 1 second. The full page can actually be quite heavy once all the ads, scripts, and media load.

We were doing this optimization more than a decade ago when I worked at HuffPost.