I trained with him at a seminar in Atlanta a few years ago. As your friend says, his technique is impressive. We did koshi waza (hip throw techniques) for almost 5 hours.
The next morning, I couldn't walk down the stairs at the house where I stayed (without help). My hips were beat into a pulp, and driving back to South Carolina was a real adventure.
When I got back, I went back to training and thought I was having trouble with an old leg injury, and trained for almost a year with a broken hip without knowing it. By the time my chiropracter x-rayed it and found the fracture, it had healed... but it was an adventure for 12 months or so.
It was the only time in all my years that I couldn't go on the 2nd day. Must be getting soft...