If the plague had been severely epidemic at the time, I would have thought the bodies would be buried closer together.
My thoughts as well. It seems a bit less random than I would expect.
“The first skeletons were laid out in neat rows, suggesting that they died in an early wave while the authorities – the then lord mayor – had made provision for the impending disaster coming from the continent.
But this is the first sign of what John Stow’s 1598 Survey of London suggested could contain as many as 50,000 bodies.”
It was the work of charity in those days to bury the dead with as much care as possible. It was considered a work of mercy. The people were unfortunate victims, and they buried them similar to their loved ones.
In our modern mindset, we tend to think of mass burials like the Nazi atrocities where people would be carelessly lumped together, however the people in London in those days were not as hard-hearted and exhibited tremendous care for the dead.
Defoe's work was written some time after the plague, and Defoe would have only been five years old in 1665, and the work is regarded as an historical novel in current parlance. However, Defoe went to some great lengths and detail to bring the impact of the plague home to the reader.
Samuel Pepys' Diary is a more contemporary writing, although I have (admittedly) not read it in its entirety.
It possible these were early victims. I suspect as the plague got more sever things got more chaotic.