advice needed

Because he's trying to figure out if you'll agree to be his side chick.

If the subject is broached, please don't do this. You'll get the short end of the stick 100% of the time.

He's being open and friendly.
You think 'open and friendly' = I've got the 'hots' for you.

The dilemma is 'your' perception of reality.

It's your 'social-programming', not your fault - You Are what you were made to be.

All's Well:)

Uh...because he doesn't want her to know about you?

I think he knows that she believes that there is no such a thing like a friendship between men and women.

Seriously, I somewhat agree with '82. Either that, or he doesn't know that she would understand your friendship.

Far be it from me to place doubt about his sincerity towards wanting to be “friends”. Friends may swap stories but not bodily fluids. FWB relationship is what he probably is seeking. This is why you’ll never meet his g/f , assuming she even exists.

Not sure exactly what's going on, but you MAY be this guy's "wingman."

Wingman is a role that a person may take when a friend needs support with approaching potential romantic partners. A wingman is someone who is on the "inside" and is used to help someone with intimate relationships.

He may feel comfortable about asking you what a female likes, and then uses that on his girlfriend.

His GF may not appreciate him thinking you are that kind of friend to him.