I don't see it. The sturm und drang of adolescence generally lingers well into the 20s. If I see relationship flailing and failing of that sort with a 20-something, I write it off as general immaturity or lack of experience. Heck, flailing/failing at most anything at that age gets attributed to that age.
I don't know of any adults who think that what they see among 20-somethings reflects on all people who do that very same thing.
When speaking of various forms of non-monogamy...it ain't poly if you're just fucking around.
While polyamory, open relationships, and swinging are all distinctly different approaches to non-monogamy, they are not mutually exlusive. Folks can, and some do, engage in more than one of them at a time--and it's all good.