Swift URL Session: Progress bar increments even with Server Error [404, 500]

Question

I have implemented a background upload task using URLSession as follow:

let boundary = UUID().uuidString
let configuration = URLSessionConfiguration.background(withIdentifier: "com.example.upload")
let session = URLSession(configuration: configuration, delegate: self, delegateQueue: .main)

var urlRequest = URLRequest(url: URL(string: "https://server/file.php")!)
urlRequest.httpMethod = "POST"
urlRequest.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")

var data = Data()
data.append("\r\n--\(boundary)\r\n".data(using: .utf8)!)

data.append("Content-Disposition: form-data; name=\"video\"; filename=\"rawvideo.mp4\"\r\n".data(using: .utf8)!)
data.append("Content-Type: video/mp4\r\n\r\n".data(using: .utf8)!)
data.append(videoData!)

data.append("\r\n--\(boundary)--\r\n".data(using: .utf8)!)

let tempDir = FileManager.default.temporaryDirectory
let localURL = tempDir.appendingPathComponent("upload")
try? data.write(to: localURL)

session.uploadTask(with: urlRequest, fromFile: localURL).resume()

To handle the server response, I have used the following code [But I am not getting any print output. Seems this method is never called]

func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: @escaping (URLSession.ResponseDisposition) -> Void) {
        print("anoop")
        guard let response = response as? HTTPURLResponse, (200...209).contains(response.statusCode) else {
            DispatchQueue.main.async {
                self.uploadComplete("Error", "Upload Server Down!")
            }
            print("error")
            completionHandler(.cancel)
            return
        }
        completionHandler(.allow)
    }

To handle the server Data, I am using following code:

func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
     if let toDictionary = try? JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? NSDictionary {
     print(toDictionary)
     }
}

To handle the completion, I am using following code:

func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
        if let error = error {
            print(error.localizedDescription)
        }        
}

Additionally, I have a progress bar which I am updating as follows:

func urlSession(_ session: URLSession, task: URLSessionTask, didSendBodyData bytesSent: Int64, totalBytesSent: Int64, totalBytesExpectedToSend: Int64) {
        let uploadProgress:Float = Float(totalBytesSent) / Float(totalBytesExpectedToSend)
        let percent = Int(uploadProgress * 100)
        DispatchQueue.main.async {
            self.progressLabel.text = "\(percent)% completed"
            self.progressView.setProgress(Float(uploadProgress), animated: true)
        }
}

This code works well if the server is working fine [Response: 200]. But if I change the request URL to a dummy url like https://server/dummyfile.php, the progress bar still increments and I don't get any error since

func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: @escaping (URLSession.ResponseDisposition) -> Void)

doesn't work.

Is it possible that in case of server errors [404, 500] the progress bar doesn't increment?