I doubt it. I just watched an instructional video to install a trailer hitch and the wiring harness had to be added during the install. Same with the fog lights, no wiring harness going back to the fuse box, although there was siring from the fuse box to the switch in the steering column (had to change the switch though). Seems to me they just install the standard equipment that comes with the van as ordered. Good luck installing one if teh harness isn't there though.
There was a post in the 3rd gen that included pictures of someone adding the NAV and RES, and there were wires in places I couldn't understand. I believe at least one and maybe both front seats had to be removed. The closest I have seen Honda come to making it convenient to add features is marking the inside of the bumpers for the parking sensor installation.