The ethical underpinnings of actual polyamory suggest that there should be a lot of mutual communication taking place, as well as a real respect for other people's relationship intentions. If he truly just wants to fuck around, he should say he's a swinger - because polyamory does actually imply having relationships of different sorts with your partners. For the most part, guys who say they are poly and don't know anything about the relationship style are doing just what she is describing - covering up their inclination to have a lot of casual sex - but give it a more respectable name. Polyamory implies a lot of self-responsible behavior, as well as deep consideration for the other people you are involved with - even if it's somewhat casual. If that's not what he's doing, he's not poly, and shouldn't say that he is.