Swinging , like Polyamory is a term that has been diluted in meaning almost to the point of irrelevance.
Couplers, is a best fit with the historical meaning of Polyamory, which at a minimum implied a stable relationship with more than two persons involved. ( Now it CAN be as little as a life revolving around one night stands, in the eyes of some)
Swinging likewise WAS a lifestyle originally involving couple/couple exchanges or threesomes with two of the people in a married relationship. Everything else was just single people hooking up or cheating.
This forum accepts more current views on each f these under the term Nonmonogamy or LS . (Remember co-opting that from our gay brothers and sisters?)
These more encompassing applications are a classic example of a larger umbrella making for less precision.
We sometimes toss terms around without bothering to pay attention to what they mean.
For instance "soft swap". While there seems to be a consensus that it does not allow for intercourse, there is less clarity on just what it does encompass.
There is a pretty broad spectrum. It extends from just watching another couple pet, to orgasms, for all, by all, involving whips and ropes. Just no intercourse.
In this light, worrying about whether or not couplers is a "REAL" swinger is irrelevant.
Her observations regarding jealousy, possessiveness, transparency, honesty along with the complexities and possibilities of multiple adult pairings, does add some color and dimension to this discussion.