.....if it is the original inlay, I don't see a darn thing wrong with repairing it, in fact, I think making a decision to deliberately leave it off makes no sense to me!

If you had a valuable piece of artwork that somehow was torn, no one would fault you for bringing it to an expert and getting it fixed. Altering means you are substantively making the item different. That does not describe what you are doing when you reglue an inlay.