IgnoreUnknownArguments does not work for values

[cdmihai]

Given the following snippet where ParserSettings.IgnoreUnknownArguments = false:

using System;
using CommandLine;

namespace Cmd
{
    class Program
    {
        static void Main(string[] args)
        {
            var parser = new Parser(with => 
                {
                    with.IgnoreUnknownArguments = false;
                    with.HelpWriter = Console.Out;
                });

            var result = parser.ParseArguments<Options>(args);
            result.WithParsed(options => Console.WriteLine(options.anInt));
        }
    }

    class Options {
        [Option('i', HelpText = "an int")]
        public int anInt { get; set; }
    }
}

And given the invocation:
app.exe bogus args

I would expect the parser to error out saying it does not understand the unknown arguments bogus args.
Instead, it does not error out.

Context: I have an optional argument (e.g. -a value) and I had forgotten to type in the argument name (-a), I typed in just the value. Instead of having the command line parser fail on encountering value, it continued working, causing quite a bit of debugging time :)