I do not see it as a flaw, unless the mission builder has the sounds  playing to "all" or "coalition" units all at the same time, that would  be problematic.   
 However, I see no issue with having different units  getting different messages according to the triggers set in the mission.  Joining multiple files into one file does not work when you have a  dynamic style trigger setup.    
As of this latest patch if they happen to occur at near the same time, one gets cut off prematurely.