Group Policy Script Processing Behavior

I've noticed that when "Run startup scripts asynchronously" is disabled, the script seems to be run in a temporary environment. When a Powershell Logon Script runs a command with "wait=false", "notepad.exe" for example, that command is run, but it's also somehow killed.

The powershell logon script I've made logs its action, so I can see it has run "notepad.exe". It run "notepad.exe" with this :

Start-Process -FilePath notepad.exe -Wait:$false

When I enable "Run startup scripts asynchronously", then "notepad.exe is run fine.

What can I do to prevent that "notepad.exe" is killed when "Run startup scripts asynchronously" is disabled ?