That just means he's old been around long enough to remember how to set up a serial port 9600,8,1,n
Jerry, I think the serial interface on the AVR is the limiting factor. The timing of the download from my laptop to the A-100 correlated pretty well to a 9600 baud connection. Now that Denon is including Ethernet ports and in the case of the 4520, a hub, it's time they rewrote the interface. That said, given the relatively low number of Pro kits out there, it probably isn't a priority.
What you say may be true, but it doesn't explain why the serial data transfer speed for the 4520 is only half as fast as the 4311. One would not expect a step backwards. BTW, I opened a case with Denon over a month ago, but (as is typical of Denon support) I have not received an answer yet.