11.2 "Install macOS Big Sur.app does not appear to be a valid OS installer application" error

[oli.mathieu]

Hello
I try to build a USB Install of BS 11.2

1. I download MacOS big Sur installer (11.2) (either via dortania's guide or with GibMacOs.command)
2. I copy the installer int the Application Folder
3. I run "sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume" command
4. I have an error : "/Applications/Install macOS Big Sur.app does not appear to be a valid OS installer application."

Any idea what I did wrong ?
thanks in advance

 

[oli.mathieu]

I download macOS Big Sur from the AppleStore and it works.