SyncRoot Property on CookieCollection class is private in contrast to Documentation

SyncRoot property that used for thread safety is not accessible. When i see the System.Net assembly, it is private property but in microsoft and xamarin api documentation it is said to be public property.

https://msdn.microsoft.com/en-us/library/system.net.cookiecollection(v=vs.110).aspx

https://developer.xamarin.com/api/type/System.Net.CookieCollection/