I see restorative yoga as meditation. A true and effortless meditation that requires no focus to control the mind. The postures can offer such comfort and ease that a contentment is experienced and there is little desire to leave awareness of the Now. A surrendering occurs.

The peace that is felt during and after a class doesn’t really come from relaxing the body but from a relaxation of the activity of the mind. 
“Restorative yoga is the use of props to support the body in positions of ease and comfort”

Judith Hanson Lasater