❔ ✅ Why does this block the UI thread?

public async void FindWindowHandle(HandleWindowFind handleWindowFind)
{
    if (!started) throw new InvalidOperationException("Process not started");
    if (playerWindowHandle != IntPtr.Zero)
    {
        handleWindowFind(playerWindowHandle);
        return;
    }

    var finding = IntPtr.Zero;
    await Task.Run(() =>
    {
        while (finding == IntPtr.Zero)
        {
            Thread.Yield();
            finding = GetWindow(_hostWindow, 5);
        }
    });
    handleWindowFind(playerWindowHandle = finding);
}