You'll find that people who practice that form of poly often need that level of intrusion into their partner's other relationships to compensate for the lack of control and additional trust your form of poly requires. I mean, sure, some people like to be highly entwined with their metamours if not dating/fucking them, but the more reasonable people only require that from people who share that desire. They are perfectly fine with their partner having totally separate relationships where no time is spent as a group with them monitoring their partner and metamour. These people won't put emotional and physical obstacles in the way stopping them having independent relationships away from the home. You'll find that the overbearing ones will try and prevent the partner and metamour having anytime away from their vigilant eyes.
These people are so reliant on this sort of close supervision, they can't imagine how anyone could navigate a polyamorous relationship without being able to step into your partner's relationship anytime you feel they've done something to offend you, or impede on your relationship. They can't imagine just beig able to trust that your partner will make the most ethical decision for all involved. They have to oversee it because of their fear (founded or unfounded) that their partner will forget them in the process.
The way to decide who would simply prefer an entwined group model and who needs It because of issues, basically, is to see who sets rules around their interaction with metamours and who simply states.preferences when asked. This rule thing works the other way round too: someone who categorically refuses to ever meet a metamour probably isn't very comfortable with polyamory