Rating details...
Honda states simply the weight of the trailer, and specifies a higher weight for boats. This would imply that DRAG is the limiting factor, and that drag would be taxing the engine & transmission more than anything else.
I suspect that the chassis/unibody is actaully not very stressed at all. As you said, the Jeep GC is similar in construction. Even the output of the engine (in some configurations) is similar.
Honda DID have problems with the 99 Ody trans, and they subsequently invesatigated the failures and beefed up components and went with the 5 speed atuo over the 4 speed --- I'd guess that the trans is still the limiting factor to the towing capacity.
Folks who tow ALOT pretty much accept that transmissions will need extra cooling, extra servicing and STILL get shorter lifespan-- while folks who PRIMARILY use their vehicel for people hauling generally won't accept this... Honda is probably going after the second group, not the first.