This isn’t true. The expansion will likely launch no later than October, probably sooner. If we generously estimate 300 days until the MCB goes to the BMAH, that requires earning nearly 17k gold per day, every day.
Chances are, the expansion will launch in the summer. Let’s say August. Again, we’ll estimate a nice round number of 210 days. That raises the requirement to almost 24k gold per day. Every day. If you miss one day, you need to get 48k the next.
I’m not saying it can’t be done. I’m just saying it can’t be done by most players with the skills they bring to the game and the time they have to play.
Still, the OP’s argument is garbage. Blizzard said their reason for removing the MCB from the vendors is because they don’t want to see AH mounts as common in the future as repair mounts are today.