Yes, there is some wizzy software in there to capture duplicates, but with anything it is a fuzzy art. It only takes a couple of characters different from the people transcribing for the software to not be sure if this is a new grave with someone of the same name or the same grave with a date missmatch. So it urrs on the side of caution and leaves both graves separate.
My advice is to make a good guess, and start photographing. Is it better to have 2 photo's of the same grave, or to miss a grave ? I would rather have 2 photos of the same grave any day. Also a second photo of the same grave can't hurt. Taken a slightly different angle or at a different time of day, maymean that it becomes more transcribeable.
If you do find that there are 2 records for the same grave you can ask for them to be combined. Just send the 2 links (taken from the address bar at the top of the browser) and email them to BG support.