I think (not sure) that I disagree with what he's saying. Groups seems like a product designed to be as easy and obvious to use as possible - all these confounding features would make it harder to use for a large number of people.
It seems like they want something more built-for-purpose - perhaps a mailing list, or even a bulletin board - and I'm not sure Facebook should compromise the usability of their product for a niche use like this.