Polyamory, especially the "open mesh" kind, dissolves the question of whether there exists a better match, or (most of) the fear of losing a partner to someone better. It's no longer necessary to consider whether this match outranks alternatives you haven't yet encountered, for both of you. It's sufficient to consider whether it works in itself.

If the hypergamy hypothesis is correct this isn't so at all.

Also consider these stats from the CDC:

Percent of all women 15-44 years of age who have had three or more male partners in the last 12 months, 2002: 6.8%

Percent of all men 15-44 years of age who have had three or more female partners in the last 12 months, 2002: 10.4%”

“Median number of female sexual partners in lifetime, for men 25-44 years of age, 2002: 6.7 Percent of men 25-44 years of age who have had 15 or more female sexual partners, 2002: 29.2%

Median number of male sexual partners in lifetime, for women 25-44 years of age, 2002: 3.8 Percent of women 25-44 years of age who have had 15 or more male sexual partners, 2002: 11.4%