Women are more likely than men to initiate divorces, but women and men are just as likely to end non-marital relationships, according to a new study that will be presented at the 110th Annual Meeting of the American Sociological Association (ASA).
And later:
Social scientists have previously argued that women initiate most divorces because they are more sensitive to relationship difficulties. Rosenfeld argues that were this true, women would initiate the breakup of both marriages and non-marital relationships at equal rate
The paper goes on to theorize that the assymetry may be because the institution of marriage (and the social expectations surrounding it) has not caught up with expectations of gender equality, leading women to feel oppressed.
And that has absolutely nothing to do with what this article is about, and certainly does not support the claimed sex-assymetry of marital dissatisfaction due to spousal changes that you claim (without evidence) exists.