About a week after submission of each update, I received an email from Apple's reviewer saying that the update was rejected due to being incorrectly rated. The apps allow "unfiltered access to Wikipedia.org, where content with mature or suggestive themes can be accessed". Unfortunately no further advice or guidance has been given from Apple, and my requests for clarification have not been answered.
The Wiki button in each app links to a specific wiki page about a bird. It is theoretically possible that from this starting point one could access mature and suggestive themes, but then it is also theoretically possible that much worse content could be accessed. So what rating would Apple like me to submit the apps? I don't know and they won't say.
I added a setting which would allow parents to hide the Wiki button, but Apple can't tell me if this will help.
I have just resubmitted the updates at a 9+ rating, with a button to hide the Wiki button, so I hope this will be enough to satisfy the reviewer. Let's hope that both updates will be out in another week.
