I know that technically polyandry is part of a complementary subset, however, the general behavior of language is that a set that divides into complementary binary constituents is named in use according to the maxim of economy: Of the subsets only the "marked" (i.e. notable, unusual) variant is fully distinguished from the parent set: So, polygynous couplings (grouplings

) aren't actually called polygynous, they're being called polygamous - since it is understood that a polyandrous groupling would be named as such (being the notable, unusual variant).
All these "gamousities" are names for traditional cultures of coupling, that's their real use, to describe traditional ways (meaning, old-fashioned, male-dominate, ownership-based) of marriage. So, well, the traditional marriage types are all particularly tasking of the female. Having that compounded by having multiple males and one female is highly likely to be worse than all the other forms of gamicity. It could be that there are some instances that aren't but I haven't heard of it.
Ironically, the multiple wives scenario is often reviled by feminists because they interpret it to mean that one man is equal to (worth) several women. They usually fail to see that in terms of traditional marriage being a work camp for the woman, having multiple women to one set of chores is actually not so bad...
Not that the specific cultures of polygynous marriage don't do their damndest to make up for and obliterate this benefit.
(Yes, I admit it, I enjoy making up these terms on the fly

)