I'm not French nor a One Piece TCG player but I live in the EU. If I were to purchase, say, figurines from my favourite anime, I would definitely not get any that didn't say 'Made in Japan'. There are too many counterfeits out there, and while some of them are really well made, they don't support the company or the artists at all - and that is important to me.
Same with Japanese music CDs - there are a billion Taiwanese bootlegs in circulation. They cost around 30% of the originals, and the covers and disks are pretty much indistinguishable from the original Japanese CDs - except the recording label will most often show 'Miya' or 'Mica' meaning Miya Records which is a Taiwanese label blatantly ripping Japanese artists and selling their music without royalties.
So yeah, for things that are meant to be Japanese products, I think it's important.