Not exactly - they are two separate triggers from your end.
Use Rufus will create and install the specific windows version you want (I always recommend taking backup and doing a clean install when changing versions)
The script you need to run separately after that. Just follow the instructions on the massgrave main website.
Could you please confirm the exact version/build of Windows 11 you're using (e.g., 22H2 or 23H2)? Also, are you part of any Insider Preview channel (Beta, Dev, Canary)? This will help narrow down why the end of service message might be appearing.