NPD gives numbers given to them from Activision, which was stated 4.4 million (you said you saw physical copies, I didnt read physical copies. I read physical + digital). It said the game created a lot of revenue, but unlike previous call of duties, this had in game purchases from day 1. So that is accounted for in revenue.
When they announce the actual numbers, it wont be near what you think it is (10+ million).
I know games have sold over 4.4 million.. thats why its ridiculous for NPD to state Call of Duty as best selling game of 2017 because its clearly not