the other stat is likely more accurate since (as far as I know) tracker.gg creates this distrubtion of their own data (which is only a subset of the total).
the other counts the number of players on the immortal leaderboard which I believe is available to everyone and officially distributed. In addition, they use the player proportions given by the official riot post.
tldr: the numbers calculated in hanafuuji's post are the populations of tracker.gg tracked players in each region which may or may not be representative of the true populations in each region.