public class ProbMap
{
    private static readonly SearchValues<char> s_values = SearchValues.Create("űßčšžć");
    private string _text = null!;

    [Params(15, 16, 64, 1000, 10_000)] public int Length;
    [GlobalSetup] public void Setup() => _text = new string('\n', Length);
    [Benchmark] public int LastIndexOfAny() => _text.AsSpan().LastIndexOfAny(s_values);
}

public class ProbMap
{
    private static readonly SearchValues<char> s_probMap = SearchValues.Create("űßčšžć");
    private static readonly SearchValues<char> s_asciiWithProbMap = SearchValues.Create("aeiouű");
    private string _text = new string('ű', 100);

    [Benchmark] public int EarlyMatch() => _text.AsSpan().LastIndexOfAny(s_probMap);
    [Benchmark] public int EarlyMatchWithAscii() => _text.AsSpan().LastIndexOfAny(s_asciiWithProbMap);
}