I would respond that sometimes sex is about sex, period. And that the causation probably runs this way: power is a means to obtain sex -- c.f., historical examples of unbridled power like Genghis Khan, who had up to 500 wives. This is not to say that's laudable, but rather to understand a point: given lots of power, men have more opportunities for sex. Which is also not to say women might be interested in the same thing, but evidence suggests they're less likely to do so. Climbing a dominance hierarchy is tough, and making it to the top is a signal -- evolutionarily, women can outsource a portion of the process of selecting a mate to outcomes determined by dominance hierarchies.
I like your point about the nature of power abuse in the workplace -- this is not always a gendered or sexually-based phenomenon, and sometimes takes a sadistic tenor.
Overall the study is great, though perhaps missing a useful connection with the evolutionary bases of the behavior observed. For example, that verbal sparring (of which gossip is a type) can be a replacement for physical conflict, and that women, being less muscular and smaller, must gossip as a form of survival. Having a lot of bigger and stronger men around means you've got to be clever.
And, sadly, our culture is full of people seeking instant gratification.