If you have read the blog
Yes, of course, that's why the blog was mentioned.
The blog follows the same route as previous Beta releases, expect in this case disabling the new file format.
This process does not work for us, starting with 10.12.6 (fully updated) new macOS VM, Parallels 12.2.1, and the latest Beta builds (tried 5 and 6).
Yes, we are downloading the Developer Seed installer from within the VM (not copied over), and yes High Sierra is downloading on the VM (not copied over).
Beginning with Beta 5, we no longer see the option to disable the new file format.
Has the process in the blog been vetted on Beta 5 or 6?
PS, before you say "Not supported'...we already know that, just asking because the blog exists and does not appear to work.
Thanks,
Don