Why is the NEHotspotHelperConfidence not nil if out of bounds?

NEHotspotEnum.playground

import UIKit
import NetworkExtension

//: First a classical enum. As documented, it will be nil if initialized with a rawValue outside of bounds
//: https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Enumerations.html

enum Foobar : Int {
    case foo
    case bar
}

if let faz = Foobar(rawValue: 4) {
    print ("Valid foobar")
}
else {
    print ("No foobar")
}

//: Now the NEHotspotHelperConfidence, defined as:

/*
    public enum NEHotspotHelperConfidence : Int {

    case None
    case Low
    case High
    }
*/

if let confidence = NEHotspotHelperConfidence(rawValue: 120) {
    switch (confidence) {
    case .None :
        print ("None")
    case .Low:
        print ("Low")
    case .High:
        print ("High")
    }
}
else {
    print ("Unknown")
}

// My expected result would be "Unknown", but it is "None". What is going on here? Is this a bug?