Semantically, this is `true` because `DoublePropertyHolder<T1, T2>` is defined as:

    public class DoublePropertyHolder<T1, T2>
    {
        public T1 Property1 { get; set; }

        public T2 Property2 { get; set; }
    }

FWIW this test is exactly the [same](https://github.com/AutoFixture/AutoFixture/blob/master/Src/SemanticComparisonUnitTest/SemanticComparerTest.cs#L379-389) with the one for `SemanticComparer<TSource, TDestination>`.