Actually the image for build 22000.1 is really downloadable from Microsoft update servers (you need some tools though to rebuild the installable ISO or ESD from a set of files, but every metadata is still there, probably because there remains instances of 22000.1 to diagnose before updating them all, and still in use by some dev labs or at Microsoft itself or one of its contractors, working on specific and complex issues).
It's not difficult to find the download and build tools on the Internet to generate that ISO or ESD, even if of course it would not be recommended now and everyone should use the build 22000.51 (or higher if it already exists for some flights). I don't know however if Microsoft will accept new licence activations with this build.