I could imagine it is a very good optimization for sites that take a long time to return the HTML of the page. Take a site like reddit, where the HTTP request

I could imagine it is a very good optimization for sites that take a long time to return the HTML of the page. Take a site like reddit, where the HTTP request can take a second or 2 to return when there is a really high server load. Reddit could return HTTP 103 hints to the clients to start downloading useful assets ahead of time so when the HTML payload finally arrives everything is ready to start execution. And if this does become a standard, it can get built into web servers and will be as simple as adding a few lines to a config file. Obviously the "correct" solution is to reduce the time it takes to return the HTML from the server, but if it can improve load times for a nonzero amount of people for not much work, it's a win in my book (even if it's not ideal).