Yes, HID Xenon lamps - that was the problem, I'm not certain but it could be that the colour temperature is different for US spec, most EU spec HID are around 4300K - which you could possibly fix by changing the burners
I got some good info (the links that you also found and some extra details) by just emailing through contact us VW.com in Germany, who then gave me the email address of sbdy at their Swiss importer, who then was very nice and english speaking. So you might want to do same with Honda.
As of today, I have a Swiss plate on my US-spec Honda. I hired a Honda garage to take it to the contrôle technique.
Front parking lights/turn signals : Parking/running lights are white (I replaced the bulbs before importing the car), turns are amber, it passed. Cars with amber parking/running lamps (normal for US cars) might have an issue. I don't know.
Headlamps : Mine are NOT e-code. The car's body color appears inside the headlamp assembly. This apparently is a no-no in Switzerland. Also, I received the car with a comment regarding an adjustment to the [shitty OEM] foglamps. They are now pointed very low. No worries; they were useless prior to the test anyway. It passed.
Antipollution/Emissions : The carnet antipollution/abgasdokumentthingy from Auto-Schweiz had only a few items on it. Stuff like air filter, exhaust integrity, OBD memory, evaporative emissions system integrity, etc. The garage checked everything and stamped the form. It passed.
Wheels/Tires : OEM wheels, front/rear tires with a similar speed-rating but otherwise mismatched. The rear tires are approaching the wear limit and do NOT bear EU regulatory markings. It passed.
Window tint: It passed with tint on the driver and passenger windows. It's a fairly light tint, but still.... It passed. This definitely should have failed the car.
Engine/chassis cleaning: My engine was quite clean to begin with. The chassis had ample dried merde de vache from my desalpes photography mission. The garage said that they would clean all of this but they didn't. It passed anyway.
Front brake rotors: Aftermarket. Cheap. Surface rust on the hats. No Swiss homologation papers. It passed.
Rear suspension modification : An aftermarket sway-bar is present. Quite visible. No Swiss homologation papers. It passed.
Wrong size battery: The factory battery is rare and expensive. This (cheaper) one is safe and secure, but I had to, uh, create some clearance for it. Not very pretty. It passed.
It seems that for an existing Swiss resident to import a car would involve a lot more hassle and expense. Cars imported as part of one's personal effects and declared on form 18.44 are actually quite simple.
I'm a happy man.
Big bump on this post.
I brought a Fiat Bravo from Italy, which originally came with H4 halogen lights, but I’ve since upgraded them to H4 Philips LED. Will this cause any issues during import inspection? It’s a significant improvement in safety, as I can now see much better. The lights themselves are functioning properly, including the levelers, and so on.