I think you could call it that. You balance your heel on the ball which supports the weight of your leg while allowing you to gently pull the leg to a better and better ROM.
Another exercise is just sitting flat on the floor pointing your toe away and then toward you. You can really stretch by doing both feet at once and pointing away with one foot as you are pointing in with the other. This stretches the back of your leg so that you can straighten the knee which is also important for ROM.
Keep working. It gets better.