[TxUmp]

So it is acceptable to give the location of the pitch - even if only the catcher and pitcher can hear it? I don't think so. What happens in this scenario?

The ump says "Ball, low". The manager asks his catcher where the pitch was. He says, "He said low". The manager who has a great view of vertical says " The pitch was not low!"

Much better to avoid the problem by NEVER calling the location of the pitch. If the catcher asks "Was that pitch low?", you just agree with him and go on.
You can get into a lot of arguments if you give routinely give the location of the pitch - and you gain NOTHING!