At the end of the day people can have whatever relationships they want. I'm not opposed to polyamory whether I practice it myself or not. I think that the SAD authors built an alternative narrative that has elements of truth in it (greater plasticity and range of female sexual desires than male, for example), but is not superior to conventional ones.
Additionally, they cherry picked data to support their narrative, by:
a. Preferring bonobos to paleolithic human relationship structures
b. Preferring bonobos to chimpanzee relationship structures (when both are equidistant from us)
c. Discounting evidence which refutes their narrative like male teste with questionable science
d. Failing to address for the different social structures between a 'tribe' or 70 or so individuals (where everybody knows each other) and modern society (where most people in the same city are strangers to us)
e. Discounting agricultural societies when they don't fit the preferred narrative, including them when they do
f. Glossing over the polyamorous details of the one actual forager society (inuits) because they don't fit the preferred narrative
I can see polyamorous behaviour working successfully in a small tribal setting (like a commune maybe)? But I can't see it working on a large scale in a much larger society more successfully than monogamy does.