Direct from RHR Manual on USB ports:
Identical Functions........


USB
Connector


It is possible to transfer audio files or pictures files to the
navigation radio. Files can be on a disc or on a USB
device (e.g., USB stick). The USB connector is covered by
a small cover which protects the connector from dust or
damage.

NOTE:


•
USB on the front of the radio and the one either in the
glove box (if equipped) or center console (if equipped)
have identical functions.
•
USB devices (e.g., camera memory USB adaptors, etc.)
must comply with the MSD (Mass Storage Device)
standard. This USB terminal can provide power to the
inserted device. The device’s current limitation must
be less or equal to 1A.

The transfer speed for this USB connector is approximately
two megabytes per second.

 

What you are prob confusing this with is, The USB, all three have the same Function as Stated in the Manual, and they have the ability to play and maybe control a Multimedia Device, always have been, well to have the iPod be part of the Menu, SAT, FM, AUX etc, that isn't done thru the USB.....and to be compatible to play thru USB, files need to be a certain format.
There are only 2 types of RHR units, Low speed and High Speed....

There were never any RHR that had a feature that another RHR didn't....oh yeah forgot, the one difference was the Mounting Frame, screw holes on top or Side, but all High Speeds work in any HIgh speed vehicle and same for low speed....making changes in control etc can be done by how wired the Harnesses are....
example..
RHR, mic is center with gray 10 way connector...

Units requiring a HFM, the mic wiring is in the gray 22 way connector....

Operating Software is by QNX, prob BlackBerry RIM may sound familiar, QNX owned by Harman Kardon.

 

Pretty sure you and I just said the same things, lol

- RHR - Comes with USB port on front, and console USB port if connectivity group is ordered. Both ports will work with iPod, USB drive, etc. with music on it and let you play music directly from the device or load to hard drive. I know on mine I have plugged my iPhone into both the console and radio front port and both worked fine to play the music directly off of it.

- RER - Comes with front USB port only. Music can be loaded to the hard drive from a USB drive via this port, but music can't be played directly from an iPod or similar attached to this port. Optional iPod cable (the 82211853 you mentioned) is available to add iPod support to 09-10 RER models, 07-08 don't work with this cable. With the iPod cable you can connect and play music directly from your iPod/iPhone.