I know it's kinda an expired convo here, but I think I know what Primus is referring to (having the fact I was born in Ukraine and seen "things" haha)
SO, he refers to "Japan" on the box being a indication of the brand origin, not where the filter was made. I highly doubt it here, but there is a foundation for this theory.
Some companies in Eastern Europe (Ukraine/Russia etc) use this trick in 2 situations (there might be more, really)
1. Convince people to pay more for a local brand. How it works - a person registers some business in Europe, then claims it works closely with a local company on a product, sells it as using a European brand.
There's a personal care Ukrainian brand (Irene Bukur) that claims to be a Swiss company, in fact all the development and production takes place in Ukraine. It's still a good brand, but I just dont like this dirty trick. My wife still buys sh#t tons of their products every time we visit Ukraine.
2. Second example has to do with politics and not related to the Honda filter, but I'll still explain
After 2014 when all of the problems between Ukraine and Russia began, Ukrainians started avoiding buying anything Russian. There was a chain of Lukoil gas stations which revenue was heavily hit because of it,
so Russian management did smth interesting. They established a brand in Romania which nobody knew, then on paper they sold the ukrainian chain to the newly created company and rebranded all of the gas stations have the new brand.
So now what a consumer sees is that Russian company quits and gets bought out by a European company. In fact nothing has changed, but business doesn't suffer anymore.
Hope it was useful, if not - at least entertaining haha.
Now back to the point about the "Japan" label.
I think Primus refers to the fact that it might be either produced somewhere in China by a manufacturer who is not related to Honda at all (fake), or even some legit manufacturer (who knows); but just to convince a consumer to buy that label says "Japan" as the origin of Honda as a brand. Again, I don't know if it's true or not, use your common sense to judge