Swift-DocC: how-to ensure that unavailable symbols for app extensions will be documented?

Swift will exclude symbols with @available(iOSApplicationExtension, unavailable) from the symbol graph if build setting APPLICATION_EXTENSION_API_ONLY = YES; is used and hence Swift-DocC won't include symbols in the documentation.

BUT Apple documentation includes symbols, e.g. UIApplication.shared, marked as unavailable in extensions.

@property(class, nonatomic, readonly) UIApplication *sharedApplication NS_EXTENSION_UNAVAILABLE_IOS("Use view controller based solutions where appropriate instead.");

How does Apple generate such documentation? Or what is the recommendation from Swift-DocC experts to ensure that such symbols get documented?

My only idea is to change the build setting before executing the documentation build, but this is certainly not convenient for developers.