It's a good idea to focus on devs in hackathons and leaving all babbling out. But "recreating a given design in html and css" is as boring as the marketing pitch.<p>That's what most unfortunate web-devs have to do all day at work :\
I actually like the concept, unlike other commenters. Sure it's not creative but it definitely is coding and I think it's the perfect way to showcase real good knowledge of Html and Css, which, unlike some people seems to believe can be enjoyed as much as backend dev or JS-Heavy web apps.
I think the goal should not be to recreate sites in the same way, but to create a better version of the same site. Hope that kind of "freedom" will be allowed and encouraged.