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.