If the blob contains requests (images, but also stylesheets, JS, or worst case fonts), it will actually instead be a net negative to latency. The browser's preload scanner begins fetching resources even before the HTML is finished being parsed. That can't happen if the HTML doesn't exist until after JS decodes it. In other words, the entire body has become a blocking resource.
These are similar conversations people have around hydration, by the by.
These are similar conversations people have around hydration, by the by.