Definitely a little strange, yeah. Feels a little like wife swapping … ? But hey, it would definitely be weird for me but I think more power to those two if that's the bond they want to share / use to measure the depth of their trust and friendship. Basically, I don't think you're alone in your response, but I think it's great that the author was willing to stick her neck out and share a personal experience with us, which I’m sure she expected to get slammed for.