Your entire post makes sense to me. I'm not sure why it is the case. It is almost as if the intimate knowledge of the other through shared experiences demonstrates their "otherness" and the more shared experiences the more this becomes obvious. This is where you have to let go of any early courtship thoughts of "soul mates", being so incredibly compatible, sharing so much and recognize the other person's individuality. I guess it is to the extent that couple successfully negotiate this that makes it or doesn't.
