Have you ever looked at your lower back position at the catch?
Every rower has a different body and has a different posture at the catch. This position and look of the body will have something to do with the way you need to be coached and rigged.
Look at these pictures and see how different the lower backs of these different rowers look at the catch. All these rowers are very fast International rowers.
These pictures prove that every rower is an individual and the rigging and training program needs to be adapted to his needs to be the best it can be. There is no a better posture than other. What is better is to be the fastest and for that you need to coach everyone to the top of his ability adapting to its needs. The goal is to make everyone the best it can be and not to make everyone to row like the model we have. Not everyone can look the same.