Yes, it IS explicitly avocating that for everyone. It's literally the whole point of the piece. It's saying that everyone should be doing those same things no matter their relationship style. What it's not doing is saying that anyone ought to give up monogamy. Everyone needs to learn to communicate and co-create their relationships as if they didn't have pre-fab structures to rely on because A) it's always better to make your relationship personal to you and B) because a lot of those marriage structures come out of patriarchy and a belief in relationship hierarchy rather than relationship partnership (the way ENM does).

TL:DR Everyone needs to learn to communicate as if they are non-monogamous. This doesn't mean everyone needs to actually become intimately involved with more than one person.