This is hilarious. While I work, one of my cats loves to share my desk chair and sleep between me and the backrest (forcing me to sit closer to the front edge). I've noticed she favors lying on her left flank there, and she is, in fact, sleeping behind me like this right now.

(Anecdotal, but +1.)

On the other hand, she's one of a bonded pair and I'll sometimes see her and her sister sleeping curled next to each other with more varied chirality. Maybe a trusted friend outweighs this effect?