autoIndexId:false support was removed in SERVER-8237 for 4.0:

Starting in MongoDB 4.0, you cannot set the option autoIndexId to false when creating collections in databases other than the local database.

https://docs.mongodb.com/v4.0/reference/command/create/

This may cause issues restoring data from previous server versions to 4.0. What should mongorestore should do in this situation?

Update: Answer: omit autoIndexId when creating collections.