My experience as a bisexual dude has taught me that men are far more fixated on genitalia than women are. I've had several guys compliment me on the size of my penis, but not a single woman has cared. I suspect that these guys are unsuccessful with women for other reasons, and are simply looking for excuses which feed into their existing insecurities.
It reminds me somewhat of incels and their various forum screeds about facial bone structure; as if to imply that women are running around like 18th century phrenologists measuring the skulls of prospective boyfriends with a pair of calipers. It's both hilarious and sad at the same time.