A similar discussion for pass by reference happened some days back.
It was for web applications however - we have concluded following.
Refer the discussion here: https://www.outsystems.com/forums/discussion/41234/are-list-records-passed-to-child-webbblocks-by-reference-or-by-value/
As conclusion by reference works on these circumstances
1. Works if modification done on child preparation
2. Does not work if modification done on child screen action
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3. Works if modification done on server action called from parent's screen action
4. Does not work if modification done on server action called from children's screen action
For mobile, we need to make observations in all such above cases for the pass by reference and pass by value (parameter passing behavior)