handleNewFlow of NEAppProxyProvider subclass isn't called

Hi! I am experimenting with NEAppProxyProvider (I just want to see the differences between this and NETransparentProxyProvider in action). I have subclassed it in my system extension and it seems like it reaches the startProxy point because I see the corresponding logs. I didn't forget to call the completion handler. However, I do not see logs about flow handling. Can you suggest to me why? Posting the extension source code just in case.

import Foundation
import NetworkExtension
import OSLog

class AppProxyProvider: NEAppProxyProvider {
    override func startProxy(options: [String : Any]? = nil, completionHandler: @escaping (Error?) -> Void) {
        Logger.appProxyProviderSystExt.warning("Starting NEAppProxy")
        setTunnelNetworkSettings(configureProxy()) { error in
            if let error {
                Logger.appProxyProviderSystExt.warning("\(#functicompletionHandler(nil)on) Unable to set settings for NEAppProxy syst ext")
                completionHandler(error)
                return
            }
            completionHandler(nil)
        }
    }
    
    override func handleNewFlow(_ flow: NEAppProxyFlow) -> Bool {
        Logger.appProxyProviderSystExt.warning("Handling flow")
        return false
    }
    
    override func stopProxy(with reason: NEProviderStopReason, completionHandler: @escaping () -> Void) {
        Logger.appProxyProviderSystExt.warning("Stopping NEAppProxy")
        completionHandler()
    }
    
    override func handleAppMessage(_ messageData: Data, completionHandler: ((Data?) -> Void)? = nil) {
        completionHandler?(nil)
    }

    private func configureProxy() -> NETunnelNetworkSettings {
        let settings = NETunnelNetworkSettings(tunnelRemoteAddress: "127.0.0.1")        
        return settings
    

Am I missing something in configuration?