Absolutely true. It’s just another piece of data to add to analyze how many are playing the game. You also can’t rely solely on sites like wowprogress or raider.io or Warcraft logs. As far as I understand, raider.io doesn’t distinguish between mains and alts; wowprogress has a limited definition of “player” for their population numbers (think you had to kill a boss on heroic nyalotha?); and Warcraft logs have to be, well, logged by players (again, as far as I understand). Each of those excludes players in their numbers, although not likely excluding many of those completing end game content.
I understand all of that. And understand an extraordinarily small portion of the player population participates in mythic raiding. It’s easy enough to go see how many CE guilds are out there. I don’t need to toss out an arbitrary statistic to show that.