DOCTYPE HTML 4.01 + RDFa

The classical W3C validator (at https://validator.w3.org/) has "HTML 4.01 + RDFa" as one of its Document Type options. If the user selects that, it then redirects to the Nu Html Checker. Is that by design?
The Nu Html Checker then proceeds to validate the source as HTML5, so that doesn't end well.
My guess is that this doctype should be handled by the classical validator rather than the Nu Checker, or that "HTML 4.01 + RDFa" doesn't belong in the list.

Pim Blokland