I think the argument they're making is that in a sexist culture all men will present with more confidence due to the belief that women are lesser. So the average woman will find the average guy more attractive...
I can't say I'm convinced.
In a culture where sexism is more common, casual sexism will not stand out at all. The average guy will not appear more attractive. In a culture where sexism is largely frowned upon, being sexist but not too sexist is an act that stands out. A man who is either not sufficiently sexist or is silently sexist (for fear of repercussion) will appear average, because that category describes the average man. The man who is only slightly sexist and is just charming and good looking enough will win out because being sexist in front of a woman is the polar opposite of lacking confidence or placing the woman on a pedestal. They reside in a cozy region between the silent/supplicant majority of men and the ones who are either disgustingly sexist or are too physically unattractive to make up for saying something sexist.
No one's saying you or anyone have to like sexism. Being offensive in spite of blowback is a confidence move whether any individual finds it toxic or not.
There are models of behavior describing personality across cultures, like Hofstede's Cultural Dimensions, that speak more broadly on the way a group behaves as a whole. You might want to give them a read.
They claimed that "being sexist in front of a woman" and "lacking confidence" are polar opposites.
They also claimed that "being sexist in front of a woman" and "placing women on a pedestal" are polar opposites.
Do you disagree with their actual claims?
Apologies for possible pedantry. I think their actual claims are actually compatible with "confidence" and "pedestal-placing" being different dimensions.