Yes, that's what I thought would happen but the only option I got there was to reload the beta. I then made a BS USB-stick and chose that in boot options instead of recovery and got told that version of MacOS was to old, I also tried that from recovery as it showed up there too but got the...
Might be an issue with M1 Macs, I got crashes when trying to open pics in Messages for one, and when trying to update to beta2 I got a popup telling me I had to be an "Owner" to update.. and the only way around that one was to do it via Terminal.
But what made me say don't, was that I found it...
The only way for me to get these betas to install, on a real MBA, is to run "sudo softwareupdate -i -a -R" in Terminal.
Maybe that helps on a hack as well?
That said, if you plan to install the beta on a genuine Mac.. don't, just don't.
Updating apps from the app store has issues on real macs with Big Sur too, seems the solution may be
Sign out of Apple ID
Close App store
Open Finder app. Go menu > Go to folder...> ‘~/Library/Caches/ '
Backup/delete the following directories: