I guess it can boil down to the range of qualities available.

In France croissants are available everywhere but you have a very high range coming from high artisan standards to very low industrial products with very basic places in the middle mostly heating stuff rather than doing the whole process.

In Japan i guess there's less available bakeries specialized in things like croissants and they sell it as a high quality product. There's also highly qualified bakers from France that are working in foreign countries.

Too much possibles biases to really judge.

That might be down to preference. French croissants tend to be crispier, saltier, less sweet, and more sour (from the cultured butter) than Japanese croissants. But you can get French style croissants in Tokyo, Maison Landemaine [0] in Roppongi even has two types, the French using imported ingredients. It really tastes like the best ones I had in Paris. I think it’s the different butter that makes the difference, I don’t think my taste is developed enough to tell the difference in flour. Both are very good.

[0] Maison Landemaine 03-5797-7387 https://goo.gl/maps/KsWoBvWk6dcyUfkq8

You're so right. I'm from Italy, and I had some of the best pizzas ever in Japan.