Marantz SR6013 receiver, HDRadio intrigue

I finally installed a decent dynalab antenna on my marantz receiver.  I was aware that HDRadio (which of course, sucks) was not listed as a feature on this model.

However, when not receiving a station clearly instead of static it seems the feed intermittently drops out, akin to a digital tuner.  With the antenna properly connected I'm not getting HDRadio self noise which I typically get on an analogue tuner in my Chicago area.

So I'm suspicious despite not advertising it the tuner dose use an HDRadio tuner.  I'm guessing they advertise it on the higher-up models to further entice a price upgrade...