我认为“你缺少的”是表达式progress.Report(++complete / total * 100)中的整数除法。当我复制这个问题时，这个表达式总是求值为零，除非total变量被转换为浮点变量类型。
除此之外，我能够重现一个模拟版本的代码与预期的结果。

public partial class MainForm : Form
{
    public MainForm()
    {
        InitializeComponent();
        buttonUnzip.Click += onButtonUnzip;
    }
    private async void onButtonUnzip(object? sender, EventArgs e)
    {
        progressBar1.Visible = true;
        Progress<int> progress = new Progress<int>(value => {
            progressBar1.Value = value; progressBar1.Update();
        });
        await Task.Run(() => FileUtils.UnzipTo("mockSource", "mockDest", true, progress));
        progressBar1.Visible = false;
    }
}
class FileUtils
{
    static string[] GetFilesMock() => new string[25];
    static void UnzipOneMock(string sourceDir, string targetDir, string file) 
        => Thread.Sleep(TimeSpan.FromMilliseconds(100));
    public static void UnzipTo(
        string sourceDir,
        string targetDir,
        bool option, 
        IProgress<int> progress)
    {
        var files = GetFilesMock();
        int complete = 0;
        int total = files.Length;
        foreach (var file in files)
        {
            UnzipOneMock(sourceDir, targetDir, file);
            progress.Report((int)(++complete / (double)total * 100));
        }
    }
}