...and what's the point here (the theory is wrong)? I can't follow your logic. I'm afraid you've misunderstood my little Porsche story.
US and Europe are two different markets. I have mentioned the UK and EU cars which actually have exactly the same specs but just a different configuration. UK "Premium Pack" is a simple "President Line" in Germany with same configuration. It all depends on the country of course, in Germany all LS 430 are equipped with serial air suspension unlike the pre-facelift LS 430 models in UK, is this correct? It was possible to buy the US LS models without the air suspension too. All the rest remained the same, same sat nav, same fridge, same motor, same everything. The only visible difference between the EC LHD and UK RHD models is the different light cone at night. So why should Toyota produce two different headlamp versions?
Yes, that's probably true. But there are three different part numbers for the front pads of my friend's Camry and other parts. And all have the same sizes and will fit his car. Toyota is not dumb and would never release a single part number for the whole world. I mean, they are not good Samaritans but want our money. Sure, you won't use the same headlamps for the US market. But here, the UK pound was very strong for a long time, much stronger then the Euro, currently the Euro is a little bit overrated, but the parts/cars are still produced in Japan and their value remains the same. Why should Toyota sell it to you or me for the same price when they can earn a little bit more in UK for example?
The actual technical/mechanical difference which is required to operate such lights correctly on my or your side must be pretty small, don't you think? What would make the production of two separate models for almost same market so difficult and expensive? I was not talking about a dashboard for example.