He lets me hug him from the back. Why does he let me do this?

He lets me hug him from the back, put my hands on his chest/ stomach but when it comes to talking he doesn't talk to me much. He can talk easily to his other female friends (he's known them longer than me) but he doesn't let them touch him like I can.
He lets me hug him from the back. Why does he let me do this?
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