As TIMOB-19844 says, both permissions are required for the new permissions APIs to work:
This guide needs updating to say you always need to have both:
To allow the application to access the user's calendar data, add the uses-permission element and set the android:name attribute to either android.permission.READ_CALENDAR for read access or android.permission.WRITE_CALENDAR for write access.
It would also be helpful to list those 2 permissions directly on:
Of course even better would be to resolve
TIMOB-7949 and then remove both paragraphs about permissions.