I see both sides of this. When a lover of tells me information of his sex life outside of me, I feel close to him. I feel an emotional intimacy between us. However, I do feel a little scared and vulnerable at the thought that somebody who is not directly my sexual partner would know what my lovemaking is like.
I enjoy a middle ground. My lovers and I do respect the privacy of sex, and we don't talk about details. But we do share general information. So I might say to Fred: "Ted and I tried using costumes in the bedroom, and I was aroused when wearing a pirate outfit." I can give Fred information about me, and how I reacted sexually to the situation. This increases our intimacy, and helps him know me better. But I don't have to go into detail about Ted's sexual response to the activity. That is Ted's information to share if he wants to.
Ted may tell me that he enjoys sex during thunderstorms. He can tell me that he had sex with Jennifer during the last storm. He doesn't have to describe the sound of her moans her orgasm face to me. That would be too personal because Jennifer and I don't have the relationship where we'd discuss that with each other.