I see nothing wrong with it as long as the horse has a little training and practice before hand.
Its a great way to safely graze unfenced pasture.
Horses also don't need chaff or any other processed feed, especially if they are overweight. My horses are ridden regularly and are on just grass with a mineral lick.
Neck collars need to be tight enough that they can't slip over the ears.
The no water is a different matter, and not acceptable.