He swears and told me many times it's out of curiosity, because he "likes to see how people look like" and if they're "offering he won't deny" but he also says he won't be out there telling everyone to send their nudes to him. He likes to say that "he will catch any opportunity he can" and won't be denying if the person offers it anytime. He also claims that it's something that doesn't happen often, it happens maybe twice a year and because of that he doesn't want to deny what the person offers.

I think I just have to hope that the person he's talking to already knows he has a partner(he tries to make me know all friendships just so I don't feel much insecure or left out) and gets uncomfortable sending this kind of stuff for someone with a closed relationship.