The article addresses a lot of the speculation about these numbers:
- This is an internal estimate that was leaked to the gaming press, and so is likely designed to be an underestimate, if anything, since it makes the entire XBox division look bad for cannibalizing their own sales (although most likely this was a best estimate).
- A whopping 82% of full-price sales of BO6 was on PS5, the one platform that does not have GamePass
- Inflated piracy numbers are addressed directly by the writer, although no specifics are given in relation to this number since the modeling was not disclosed
So, I think a lot of other commenters are unreasonably dismissing this number as inflated when it's likely fairly accurate.