No, there is no reason for that, and yes, for consistency reasons you can insert the value from your download of the spreadsheet. Maybe there was a difference in a different spreadsheet for the method 5 years ago, I don't know. The difference is 0.02%.
You could also round both values to 8100 and then they will be equal. Of course the values should be used consistent, but 4 significant digits or more might be overrated. It's a simple ratio of world emission estimates and world population from old official data. Also in the new EF 3.1 the official normalization values slightly changed compared to 3.0, because some characterization factors changed, but world population and total emissions are still based on the year 2010 data as far as I know.