I've never heard it, but it may be because no one had the nerve to say it to me. Bimmer sleeps on the floor at the foot of the bed, Kharma sleeps next to him, and Shiva either sleeps on the floor at the side of the bed, or goes back to the living room to snooze on the couch after we've fallen asleep.
All of my German Shepherds have slept beside my bed, with their heads toward the door, or just inside my bedroom door, on guard. When it was just Bimmer and me, he slept up on the foot of my bed until I fell asleep, then would lay across the doorway. Purdue, my first GSD, slept on the floor by my bed until my parents went to bed, then crawled carefully up on the bed. He was slick enough to get back on the floor before anyone came downstairs to wake me up in the morning. (lol) So far, I've had no dominance issues whatsoever, even with Bimmer who's part wolf, or with any of the Filas.
I think dominance problems stem more from owners' and dogs' personalities and lack of understanding than from where a dog sleeps.