Can't get "shortcuts sign" to work

According to the Shortcuts User Guide, the following command should sign a shortcut:

shortcuts sign --mode anyone --input "Share me.shortcut" --output "Share me signed.shortcut"

I have tried that formulation but get this error:

Error: The file couldn’t be opened because it isn’t in the correct format.

So, I tried to sign an exported shortcut:

shortcuts sign --mode anyone --input /Users/[Home]/Test.shortcut --output /Users/[Home]/Test-signed.shortcut

That returns nothing suggesting there was no error. But codesign says:

/Users/[Home]/Test-signed.shortcut: code object is not signed at all

Is code signing working for shortcuts ? Is there a way to sign a shortcut ?

Can't get "shortcuts sign" to work
 
 
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