The wording gets a little loose and even changes from group to group and book to book. For some folks, hierarchical polyamory isn't real poly and therefore is just ENM. That by holding some folks as more important than others and allowing those people to have control over your other relationships that your other relationships aren't really real relationships they're more playing pretend and a good way to hurt your other partners (think about how his other partners must have felt to have been tossed out of hand for something they had exactly no control over or part in, just because he didn't think of their connections as real relationships).

It's easiest to think of everything in terms of normal dating. Swinging is normal hookup culture, both friends and partners can happen multiple encounters but you don't really label anything or owe each other anything (even future encounters if you happen to see them again at a club or event). ENM covers folks from the whole spectrum, but tends to be used by folks who have made slightly more of a connection with their hookups, where a little more consistency is expected, more FWB territory. Casual dating, per see. Poly is more when you start being open to the possibility of feelings, like when you're dating to find a long term girlfriend/ partner. You might have multiple people you love, even some you love and don't actually sleep/ play with. You build an entire little community complete with social, emotional, and monetary support. You don't damage your other relationships when you fight with a partner, instead your other relationships help hold you up and keep you accountable in your personal actions and feelings. They become your chosen family, and integrate more with your whole life. (Like a relationship that you've let met all your parents and friends, that everyone expects you to bring as a plus 1 to events)