I think they want the social aspects of a bunch of people doing the course and having discussions/QA on the course forums. Personally I found visiting the forum

I think they want the social aspects of a bunch of people doing the course and having discussions/QA on the course forums. Personally I found visiting the forums during the ML course last year to be pretty depressing. seemed to be a mix of entitled whining and nauseatingly giddy excitement, both of which killed my learning boner. Overall great experience though.