I agree, although I think that it would be fairly easy to add a “remove this account” button as well. This would mean erasing personal data from the user and user_settings table and disabling the account. I think that removing the whole account (row from the users table) would cause problems. You would just end up having an user X who has done certain things in the past. Of course there is the option of merging, but with which account?
But this can not include data in the authors tables. I would compare this data to the data maintained by libraries. I do not think that GDPR can mean that an author can demand that her personal data (name etc.) is removed from a library database if she has authored a book.