There is a setting, "Jazz Down the Chords" that might help if you are looking for classical or simpler harmonies with the chord reharmonizer.
However -- and I'm sure that you know this -- there exists many differing combinations that will work with the same melody. I think that is all the reharmonizer is capable of coming up with at this time. It isn't smart enough to know that you are wanting, say, only classical chord theory to apply, or that your chosen genre is a hymn that has certain rules governing the underlying harmony.
It is what it is, and it can indeed be quite useful in certain situations.
If you want to try to use it in a fashion that it is not designed to be used in, or get it to do a job that it is not designed to do, ie nail an existing chord change for an existing hymn, and then knock it because it cannot do that, you are correct in that there is nothing more that need be said.
--Mac