I disagree with this comment. If anything the video shows that the HTML5 version here does not lose state when moving between feed and wall. So in effect, it consumes less data when used.

Also, FB is an online community so there is no way to get content, whether native or HTML5 without data plans on your phone. While the native app will be able to cache some content, FB will never make it large enough because they want to get site traffic (and hence ads)