Ok sorry for spam.
I changed the UCLASS(config="Game")
macro to use a custom name:
UCLASS(config="MyPluginConfig")
And I verified that when I toggle the test boolean it DOES create the .ini file:
Saved\Config\WindowsEditor\MyPluginConfig.ini
The boolean is saved as True, but when I reload the editor, the property is false in editor settings.
;METADATA=(Diff=true, UseCommands=true)
[/Script/MyEditorModule.MyUserSettings]
bTestConfig=True