Instructions for installing macOS 15 guest don't work

I tried to install a Mac OS 15.0 guest (release, not beta) on a Mac OS 14.6.1 host (Apple M2 Max, Parallels Desktop Pro 20.0.1), following these instructions, but they don't work:
Install macOS virtual machine on a Mac with Apple silicon

I downloaded "UniversalMac_15.0_24A335_Restore.ipsw" from here:
https://developer.apple.com/download/

Following the instructions in the article, I opened that .ipsw in Parallels Desktop. It created a virtual machine in Desktop, but when I tried to run it I got:


Clicking Install produces this error:


Restarting the host Mac didn't help.

I was able to install a Mac OS 15 guest by doing Parallels Desktop > New > Download Macos, which installed Mac OS 14.6.1, and then doing a Software Update in the 14.6.1 guest. But I had been hoping to avoid the extra download and install of Mac OS.

 

Installing the latest version of Xcode might solve this issue.

 

What might Xcode contribute to Parallels' creation of virtual macines?

 

I think it contains the "software update" that "is required to install macOS in a virtual machine."
I saw the following on Apple's release notes:

 

I wonder if I was tripping over this bug that was fixed in 20.1.0:

"Fixes the issue that resulted in ISO installation images built for Arm architecture erroneously designated as incompatible during the VM setup process;"​