This position doesn’t look all that practical for vigorous thrusting, but it does have a pleasing visual symmetry. I can also imagine that the full body contact combined with the penetration would be wonderfully erotic and intimate. As he breathes and flexes he’ll feel her weight on him and in him.
This image is originally from the rather excellent Strapon Dreamer site. I found it via the Badkitty Kat tumblr.