I'm having difficulty understanding why there are two locations for enabling automatic app events for iOS in the Facebook dashboard.

The first location is located in the [my Facebook app] > App Settings > Basic > iOS > Log in-app events automatically (recommended). This appears to be only a on/off option.

The second location is located in Events Manager > Data Sources > [my Facebook app data source] > Settings > Automatic event logging for the Facebook SDK. This has the options of on/off/unspecified.

When modifying one setting, the other setting does not seem reflect the made change.

What are the differences, if any, between these two settings? Why are there two locations?! And what are the consequences of not enabling one or the other?