WatchOS companion app Builds successfully but gives WCSessionDelegate error when Archiving

Question

In the WatchOS companion app I have this model:

import Foundation
import WatchConnectivity

class WatchViewModel: NSObject, ObservableObject {
    var session: WCSession
    @Published var counter = 0
    
    // Add more cases if you have more receive method
    enum WatchReceiveMethod: String {
        case sendCounterToNative
    }
    
    // Add more cases if you have more sending method
    enum WatchSendMethod: String {
        case sendCounterToFlutter
    }
    
    init(session: WCSession = .default) {
        self.session = session
        super.init()
        self.session.delegate = self
        session.activate()
    }
    
    func sendDataMessage(for method: WatchSendMethod, data: [String: Any] = [:]) {
        sendMessage(for: method.rawValue, data: data)
    }
    
}

extension WatchViewModel: WCSessionDelegate {
    

        public func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: Error?)
        {
        }


    
    // Receive message From AppDelegate.swift that send from iOS devices
    func session(_ session: WCSession, didReceiveMessage message: [String : Any]) {
        DispatchQueue.main.async {
            guard let method = message["method"] as? String, let enumMethod = WatchReceiveMethod(rawValue: method) else {
                return
            }
            
            switch enumMethod {
            case .sendCounterToNative:
                self.counter = (message["data"] as? Int) ?? 0
            }
        }
    }
    
    func sendMessage(for method: String, data: [String: Any] = [:]) {
        guard session.isReachable else {
            return
        }
        let messageData: [String: Any] = ["method": method, "data": data]
        session.sendMessage(messageData, replyHandler: nil, errorHandler: nil)
    }
    
}

I can Build the app successfully and run it on the simulator. But when I try to Archive the app I receive the error:

Type 'WatchViewModel' does not conform to protocol 'WCSessionDelegate'.

The error message makes it sound like my WCSessionDelegate is missing a required method, but I can't seem to find it.

But why does it run on successfully on the simulator then? Also, if I change the Archive scheme to Debug instead of release, then the Archive is successful.

I'm stuck. I do not know how to track down why this error would happen in Debug scheme but not Release. Can anyone point me in the right direction?