I'm informed that it's not a Vesa mount.
It's a Vesa adaptor.
Your $5k or $6k monitor needs $200 spending before you can attach it to a Vesa mount.
Which is sold seperately, and not by Apple on their page.
So you are right that third party Vesa mounts won't be available straight off, and would you really want to trust your new, expensive and very heavy monitor to a third party adapter?