Fair point in pointing that out but I believe the documentation is not sufficiently clear based on the position of the VyOS team discussed in other posts about LTS images.
I believe what they are trying to say in the documentation is that you can build an image from the LTS branch at any time but not that you can build the same release image that the VyOS team release to paid contributors.
Related discussion: Getting LTS as a lowly single user - #23 by Apachez