I strongly dislike the entire idea of a honeymoon registry. If I am going to give the couple money for their honeymoon, I can simply hand them a check with "For Your Honeymoon" on the outside of the envelope. That way 100% of my money is spent on them, not diverted to a third party.
As an alternative, I can always phone or look up the website of the honeymoon locale and see if there is a gift I could have sent to them directly. Again, no unnecessary fees to a third party website.