The users don't empty the trash, the admin does. This particular EBA does not empty the trash, as there are often notes that need to be recalled from the trash, by the admin. When a user joins a notebook that has been used for a while, they also get all of the trash for that notebook.
1. User is invited to the notebook 2019 10 01.
2. User gets all of the notes currently in the notebook, AND every note that has ever been deleted from that notebook, since the notebook was created, not just since 2019 10 01.