I don't really know the intricacies of how the BB-training site manages holes in the data. My expertise was really in turning the analysis into a usable spreadsheet. But I do know that the site has gathered enough data and the analysis is good enough that it "weeds out" bad data. And there's a plethora of data on 1v1 especially. (If we were talking SB, that might be different story.)
If you're worried aboutit, it's possible for you to go back in and fill in those holes as long as they are still on your buzzerbeater site training page. Just click the "Send to BB-Training" button next to an old training instance (assuming you've downloaded and installed the add-on.)