A little harsh, don't you think? The link is to a blog post - not a landing page - and it seems to me it can contain whatever the author wanted it to. The post wasn't submitted here by anyone from &yet, but by Jeremy Ashkenas (the creator of Backbone which is partly the basis for ampersand).
The actual landing page is http://ampersandjs.com (linked in the first sentence of the blog post) and has plenty of technical content like the user manual/guides you wanted (http://ampersandjs.com/learn) and api docs (http://ampersandjs.com/docs).