It doesn’t help that the article itself mixes in the concept of threesomes with poly. One is, in the usage I have encountered so far, refers to a sex act with t

It doesn’t help that the article itself mixes in the concept of threesomes with poly. One is, in the usage I have encountered so far, refers to a sex act with three people, while the other is a relationship type. You can have a poly relationship without ever having more than two people in the same bedroom at the same time. And of course you can have a threesome without being in a polyamorous relationship. Mixing the two concepts does not help clarity at all.