The issue from what I've read is that pinning down excess deaths in the last ten years to specifics is difficult. All the authorities on the subject acknowledge they're dealing with estimates because it's complications from flu which cause death, so it's difficult scientifically to pin that to the virus which set it off. As a result, data seems always flawed.
I'd suggest that's why there is still argument on the subject. You can go with best educated guesses, but there's wriggle room because as a nation we never really cared that much about excess death in the old and infirm till this year.