It absolutely doesn't work for me. I see the Mojave DB7 in the link you posted. When I click on it I am asked to sign in with my Apple ID. I then sign in with the same Apple ID I used to join the public beta program and then it gives me a new list of downloads that only shows Xcode 10 beta 6 and Xcode 9.4.1
I've tried this now from both High Sierra and my Mojave install. No difference.