I'm pretty sure there's another way to buy pubg on pc. Going off the Europe and Asia leaderboards I estimate(paper napkin estimate 😀) it's anywhere between 1.5-2 million on Xbox. Also they announced 1 million players after 2 days which is more inline with my estimate than yours. In either case it's selling great.
Halo MCC will sell 5+ million copies(including digital)
halo 5 will sell 10 million copies(including digital)
x1 will pass ps4 in USA, and UK.