Settings Bundle observing in NE targets

Hi, I have been trying to add Settings Bundle to my app that utilizes DNS Proxy and Content Filter, however, I noticed some weird behavior. I worked with Settings Bundle before, but the initial implementation didn't work for some reason.

So, I simplified it to just one toggle switch and tried again.

Initially, I had an observer adding in the init of my SettingsBundleService class and I was using a shared instance in DNS Proxy target, as a result, SettingsBundleService was observing changes but would always return false. But when I tried to use a shared instance from the main target, it worked just fine.

public final class SettingsBundleService {
    static let shared = SettingsBundleService()

    private (set) var test: Bool = false

    init() {
        registerSettingsBundle()
        NotificationCenter.default.addObserver(self, selector: #selector(defaultsChanged), name: UserDefaults.didChangeNotification, object: nil)
        defaultsChanged()
        
        Logger.statistics.log("[SettingsBundleService] – added Settings Bundle observing")
    }
    
    private func registerSettingsBundle(){
        let appDefaults = [String: AnyObject]()
        UserDefaults.standard.register(defaults: appDefaults)
    }
    
    @objc 
    private func defaultsChanged(){
        self.test = UserDefaults.standard.bool(forKey: "enable_feature_preference")
        Logger.statistics.log("[SettingsBundleService] – changed: \(test)")
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
        Logger.statistics.log("[SettingsBundleService] – removed Settings Bundle observing")
    }

Could somebody advise me on what I am doing wrong here?