But it wouldn't be conventionally ev-psych cynicism to suppose that you don't really love your mate, and that you were actually just attracted to their body all along, but that instead you told yourself a self-deceiving story about virtuously loving them for their mind, in order to falsely signal commitment.

Why would loving someone for their mind be any more virtuous than loving them for their body? Not liking stupid people is usually considered more arrogant than not liking ugly people.