Hmmm. I like the idea of only one rise.
His fire looked safe to me. We can't see if it was damp ground or not, he had a shovel, and the fire was kept small.
Not using a rock ring is more of a Leave No Trace method. Then, after the ashes are good and cold and wet--I presume a creek was nearby, you work them into the ground, sprinkle some needles or leaves over, and it looks like no fire was there.
The traditional rock ring is good to put a rack across, rest feet on, put things on to keep warm. It can supply excitement if the rocks explode. It doesn't keep a fire from spreading. Raking the leaves and fir needles out from the fire area will do that. And not burning during a wind storm or dry conditions will also help.
On one camping trip, the woods were dry and the wind was blowing in from the east, so we only lit some small candles for our "fire". They were on top of a rock. It worked. It wasn't cold so we survived.