Romance is a journey about people finding one another.
Classic erotica is one person's journey to self-fulfillment through sexual expression and exploration.
When we put the two genres together... it's a journey that leads us to both our heart's desire and our self-actualized personal best, all because we expressed our deepest sexual self with the person we love and formed a bond meant to last through either a meaningful encounter or the rest of our lives.
I think this is beautiful and well-put, and it emphasizes how well the genres can support each other when used in tandem. Of course, they don't have to support each other, which is why there's still a place for each on its own. Romances don't have to be consummated at all, and I would argue that some friendships follow a classic romantic arc. Sexual exploration can open and transform a person even when no bond is formed with anyone else, or even in the event of negative emotions with sexual partners.
I do have to say, however, that the erotic romance journey Black describes is very much what I want to experience with a partner, and represents my personal ideal of romantic love.