And I think that with an 9 tooth drive gear, the car doesn't neet the adapter at all (like John's car).
That would be my guess as well. I don't have any data on 9 tooth drive gears utilizing a reducer. Each transmissions has a part# tag that designated its build configuration. If 9 tooth drive gear transmissions did not need adapter/reducer in high numerical gear applications then why wouldn't they install transmissions configured as such based on the part# tag. Assuming that the pn tag/brass tag in fact provided a configuration/BOM for the trans.