A long time ago Coach Sommer responded on this. It was something to the likes that he doesn't employ the ring dip to elbow lever/pseudo maltese-planche.
Gregor did note that this was a basic exercise he used in training for maltese. Basic as in for beginners.
The korean dip does basically the same thing as the RTO dip except it is not on the rings but it's on PB. There are two variants using two different grips (over/under).
Korean dip is a pain if you have a big posterior chain. It just won't fit around the PB single rail. I'll probably set up some blocks to do them tonight at the gym or just wait until I am strong enough to do them on rings again. I can do them on short straps but not our straps at the gym that hang from the ceiling.