Unable to sort items with custom TypeDescriptorFactory

I would like to have very granular control over sorting. So I've created a custom attribute called SortRank, which takes an integer. I realize that the documentation says that SortImportance is considered, and then DisplayName, but under the help, under "Building a Custom Factory", there was this glimmer of hope:

"By deriving from TypeDescriptorFactory or TypeReflectionFactory, the custom factory can customize the items or properties already generated by these factories. Such as adding or removing properties, categories, or category editors, or rearranging the items."

Is it possible to sort like this? If so, what am I doing wrong? I am including my derived class -- it's very simple:

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public class ExtendedTypeDescriptorFactory : TypeDescriptorFactory
{
protected override IList<IPropertyDataAccessor> GetProperties(object value, DataFactoryOptions options)
{
var p = base.GetProperties(value, options);

if (p == null) return null;

var result = new List<IPropertyDataAccessor>(p.OrderBy(prop =>
{
var rank =
(Window1.SortOrderAttribute)
value.GetType().GetProperty(prop.ValueName).GetCustomAttributes(false).
FirstOrDefault(x => x.GetType().Equals(typeof (Window1.SortRankAttribute)));
return (rank == null) ? 0 : rank.Rank;
}));

return result;
}
}