As I understand it, the kit is based on the model the Smithsonian commissioned quite a few years back and the carvings duplicate the ones on that model. I believe the plans for it were done by George Campbell, an extremely knowledgable an conscientious researcher, back in the 1960s (or maybe a little earlier). He clearly relied heavily on the "Isaac Hull model," now in the Peabody-Essex Museum of Salem, Massachusetts, which I mentioned earlier in another thread. I haven't looked at that model for quite a few years, but I suspect the carvings on its stern are pretty crude. (All the other woodwork on it is.)
As you probably know, the Constitution has undergone lots of changes during her career; about the only thing we can be sure of regarding the decorations she wore during the War of 1812 is that they didn't look much like the ones she wears now. Any attempt to reconstruct her appearance during her glory years has to rely on research and guesswork.
In recent years some enthusiasts have cast some doubt on Campbell's work. That's probably inevitable, and no reflection on him; our understanding of historical subjects is always changing and, we hope, improving. I haven't read anything specific about the carvings. You might want to get in touch with the ship model club that meets at the Constitution Museum; I think it may have a website. (Another way to get in contact with it might be through the Nautical Research Guild.) I suspect the folks in that club have studied this subject pretty thoroughly.
I have a lot of respect for Campbell, and almost as much for the first-rate artisans at Revell who made the masters for those carvings. My inclination would be to leave the carvings as-is unless I found a mighty convincing reason to change them.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.