Your girlfriends will give him even more insight into who you are as a person.
He is excited about you. He likes what he has been experiencing so far into this new relationship.
He wants to learn more.
He wants to be certain that the girl he is believing you to be is for real. Your girlfriends will help to confirm that once he gets to know them.
When a guy is keen to get to know your girlfriends and is wanting to meet them, it is often a good sign that he is beginning to look at you as a potential long-term partner and he is now looking to your girlfriends to vouch for you.