Why would a guy think he gets along better with women and find it easier to be friends with women?

I'd say 80% of colleagues in my field of work are female.
Maybe his experience is similar.

Many of my generation were raised by single Mothers and female relatives.

And if you're in my age range you'll have gone through strong, independent women at home to many in education.

We as teens/20+ers went through a whole raft of anti-discrimination workplace training days back in the 80's specifically to ensure things like 'acceptable physical and verbal' behaviour was drilled into us because no employer wanted sex discrimination court cases.

I used to be that way actually but I'm getting to the point that friendship is one thing trusting beyond that though it's a whole another ball game

Probably raised by an oppressive single mother and has more or less been emotionally castrated. He's likely completely devoid of masculinity.

Because I grew up around more women than men. Men will still invite me into their circle and I give off alpha vibes but I’m more of a sigma.

I don't know if "easier" is right, but most of my better friends are women.

Perhaps he grew up with only sisters