This follows Denon's pattern of progressively rolling out firmware changes.
While infuriating at times, it does have an upside, as it limits problems the new firmware might introduce to just a few users rather than the entire installed base.
Regarding on-line vs USB (or other physical media) distribution of firmware:
While one can disagree with Denon on the on-line only firmware distribution, I actually agree with it. As over the long-haul, it ensures the installed base is on known, stable releases.
It also has the huge benefit of providing them with objective data collected from the units in the field about configs, errors, and other information that they can then analyze to improve firmware, product designs, etc.