I only read the abstract, but I notice it's mono-biased. Basically, it presupposes that humans are monogamous and attempts to explain why.
They measured perceived attractiveness of partner vs non-partner women, both familiar and unfamiliar, under the influence of oxytocin. They did not measure attractiveness between multiple bonded partners, or between a legitimate partner and an infidelitous partner.
I couldn't access the full article through my university, but I'd be interested to see the numbers on the partners vs familiar vs unfamiliar women. They found that men are more attracted to their partners than to other familiar women, but the abstract didn't provide the margins or comparisons with unfamiliar women.
In my opinion, the findings are more indicative about what hormones are responsible for pair-bonding in males than they are about explaining fidelity or demonstrating a biological basis for sexual monogamy.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker