The problem is that we always have to compromise between having a clear, easy to read chart (that follows standard music convention) and a chart that can be played as intended by iRealPro player.
I usually put the priority on having a clear chart that anyone can sight read.
The idea of the outro rehearsal mark is simply because there way iRealPro is handling the coda is not standard.
Usually the coda finishes the song. It should never go back to any part of the song once the coda has been played. Third endings is the way to go, but it doesn't work always as intended. I had some situations where the player just skipped the 2nd and 3rd ending (in a repeated section for example)
If the coda system were acting like a real coda, many problems would be solved.
I just think that if the developers would spend time to fix a couple of things regarding the coda, repeats, endings, we could have a fully functional​ player.