I actually had the same thought, but I also get that some people don't like HTML-based templates for various reasons. My next thought was whether or not you could just augment this framework by providing a utility that converts an HTML-based template into the view that mithril expects and make both camps happy. As an optional contrib module, of course -- I'm not suggesting he start heaping on additional framework features already. :)

edit: I just wanted to add that I read through the guide expecting to find yet another half-baked framework but the whole thing seems well thought out and I like the philosophy alluded to in the guide. I'm definitely going to try this for my next mini-project.