TLDR: Good news, those instructions worked for me!
Notably, I followed those instructions twice, the first time for my existing project and the second time from scratch using your steps (including selecting the 'Mac app' template)
It seems the only different between my setup and yours:
I use the macOS > App template
Whereas I was using the 'Multiplatform > App' 😬
I've filed a bug report under number FB16853042 for this via Feedback Assistant linking the above threads too.
Also, OOI, where is your XcodeZone
folder? I'm wondering if I should keep my main Xcode in Applications and keep the betas / older versions in another part of disk just to prevent any other weirdness (I've seen things like this before where multiple Xcodes can conflict)