It's also a question of whether the actual DR components are able to make a difference in the Nova. There are plenty of Naim Classic and XS range items that do have space for these but they are not used.
The thing is, as you go further up in turns of hifi (anything, not just Naim), in order to reproduce music more faithfully and draw out the subtlest nuance buried in each recording, everything needs to become both sensitive to pick up the microdetails and then all the way down the chain to the speakers to not lose information that is extracted. That comes at the cost of more expensive hifi being fairly tweaky (sensitive to cables, placement, temperature, vibrations, RFI etc.). It could therefore be argued that DR components are added to units that will actually benefit from them. Thus the added but modest cost of adding DR to things that probably cannot benefit from it, is not passed on to the customer.
Of course, I should state emphatically, I have no actual idea at what level DR benefits stop being audible. For all I know, it could make a huge difference everything. But I suspect that is not the case.