Well, you know that I've been posting for years that I did not think Harry really loved Murphy. I mean, he cares a lot for her, and definitely loves her, but not LOVE her. Then PT happened, with a True Love that surprised me. And then, she died. So my idea is that, from a literary point of view, the only reason why JB included True Love is for giving Harry a protection from whampires. That way he can even be married with Lara and still not have sex with her. (Of course, something can happen that prevents the wedding for happening at all but anyway). It will also explain that Lara does not have sex with him during courtship.