This isn't what the OP was asking, but I was wondering if the label "play partner" has more positive connotations than "fuck buddy." (It sounds more sex-positive, anyway).
Poly people who are also kinky often talk about having kinky play partners as part of their relationship networks. (Not all poly kinky people, obviously, but some!) A high level of trust and intimacy is required with a kinky play partner, even if you never fall "in love" or never do anything together that isn't sexual.
For me personally (I'm not quite vanilla, but I'm not really kinky either), I had such a wonderful experience having a "fuck buddy"-type relationship in my mid-20s that I can't imagine denying anyone the freedom to seek out that sort of thing. I suppose we were more friends-with-benefits because we did very much like each other as friends, but in truth we didn't have much in common as friends. We didn't have any reason or desire to hang out as friends. I went to his plays, he read my writing, we occasionally got together for sex. We never developed romantic feelings for one another, even though we were involved for almost 4 years.
He's the only past partner of mine (sexual or romantic) whom I keep in touch with and think of fondly. He was a much more positive force in my life than other men who had "loving" relationships with me.
So that experience has certainly shaped my approach to relationships.
Single, straight, female, solo, non-monogamous.