https://chartmasters.org/2021/…-bit-of-ifpi-annual-list/
TL;DR: They touch on how many releases from Asian artists are excluded on the list, such as Lit by Lay(sold 2.65M units in China), New World by Hua Chenyu(sold 2M in China), Resonance by NCT(sold 2.6M combined), Neo Zone by NCT, Heng:garae and Semicolon by SVT, and Delight by Baekhyun
They also touch on how Chinese sales were obviously counted for some artists(such as Justin Bieber for Changes), but not reported for others (like BTS BE, Taylor Swift's folklore/evermore, BLACKPINK's The Album and Eminem's 'Murdered To The Music')
They also mention how IFPI clearly used different methodology for all three BTS albums. Only counted Gaon sales for BE, added Chinese downloads for MOTS: The Journey, and something else entirely for MOTS7.
Here's what they think the actual list should look like:
Dying at the fact that Justin, AC/DC and Taylor are the only Western artists in the top 15 djjmbjgxd