The standing reach-up back rotation stretch does specifically mention the back but it can also stretches internal and external abdominal obliques. It will also help relieve tension in your lower back, where your quadratus lumborum is located and stretched in this particular stretch.
Don't ever under estimate the importance of stretching and the benefits it holds.
The standing reach-up back rotation stretch is beneficial for back muscle strain, back ligament sprain and abdominal muscle strain.
Always remember that while stretching may be recommended to aid recovery out of injury, you should always be very careful when stretching through rehabilitation. Your soft tissues are likely to be more vulnerable to re-injury if you stretch too much or too hard during this time. Always check with your Health Care Professional who is guiding you through your recovery to make sure it is appropriate to start stretching, and please - ALWAYS FOLLOW THE RULES FOR SAFE STRETCHING (The first posting on this stretching blog).
Image taken from "Upper Body Stretches" wall chart by B. Walker.