That is indeed a very interesting example.
It's not uncommon to have a memorial in one cemetery and the actual grave in another. That's especially common with war memorials. But what you have here definitely does look like two proper graves, not just one grave and one memorial.
Obviously he can't be buried in two places at once, but I wonder if he was cremated, and his ashes have been interred at two separate locations? This could happen if his family couldn't agree on where he should be interred, or if he had loved ones at two different cemeteries (say, his paternal grandparents at one cemetery, his maternal grandparents at the other), and his family wanted part of him to be with both, so to speak.
As for what you should do about it on BG: what you really need (and I have suggested as an enhancement), but we don't have yet, is the relationship of Self, to go with Spouse, Child, Parent, Sibling, and the rest.
In the meantime, I suggest you write something in the Grave Description sections of both graves, and include the URL of the other grave, similar to what I have done with my policeman cousin John Collins. He died in 1911 as a result of injuries received on duty. He is recognised on the official police memorial at Springvale Cemetery, and he is buried in an unmarked grave (which I was able to identify) in the same cemetery. I can't merge them (and I don't want to) because they are not the same grave, and I can't link them directly because there is no Self relationship, but I did provide full details in the Grave Description section. More details here: http://community.billiongraves.com/5162/pictures-transcribe-normal-headstone-military-headstone?show=5165#a5165