That finishing position from Ma Long and Rich is a salute position. If you finish with a salute position, with the upper arm largely on the same side of your body, that is fine. Your practice video did not reflect a salute position.
The main issue isn't so much where the arm finishes but how the body was used to move the shoulder joint through the stroke. Using the upper arm a bit is inevitable, but the temptation if you are learning is to *use it more*, when the way to get power is to use the core/whole body to move the shoulder joint so that the upper arm works less (it still works, but it shouldn't be where you are getting most of power). A Salute position usually is a good sign that you are not overusing the upper arm. Not a perfect sign, but usually a good sign.
First of all, Ma Long is playing further back from the table than you are. If you focus not on just the still shot of the finishing position and you look at the whole Ma Long stroke, he rotates his torso over his right knee to power the backswing stroke. *Not his upper arm*. So he is hitting the ball with his whole body. Dima who is taller, is doing the same, he just isn't getting as much leverage because he doesn't use the arm the same way.
If you look hard enough, you will find shots with Quadri Aruna and a few other players finishing with their upper arm wrapped over their heads on some shots during rallies. This is not *Base* technique for most of these players. Everyone makes compromises or slight changes to base technique to adapt to certain balls. But the base is usually a standard stroke vs block, powered mostly by using the torso/core/legs with a good finishing position for recovery.
BTW, there is nothing wrong with arguing, in fact, I sometimes hesitate to bring in video of good players hitting the ball because it can give very wrong impression and there are some very good player who hit the ball their own way, mimicking them with their fitness level and technique is often asking for trouble. As long as your technique is not causing injury and is using a kind of helicopter motion, there are many options. But what isn't correct is using the upper arm in isolation from the body and swinging upwards with the upper arm is usually a sign that something has gone very wrong in figuring