I didn't watch the video but I have a personal story to relate.  Sometimes my lower back hurts because of sitting in a poor posture. Sleeping on a bed no matter how firm just makes it worse.  But sleeping on the carpeted floor fixes it and in the morning I'm magic again.  Yes, it hurts to sleep on a hard floor. But my back somehow needs that. I wouldn't do it if it didn't work, and I only do it when my back is hurting.