Ha. Can confirm. Lived there 2 years and while I love the food, as far as I can tell there is no food available anywhere in Japan, at all, that the average south east asian would recognise as even mildly spicy. And outside the home islands I have observed Japanese people reacting hilariously to the actually spicy local food. My favourite was a co-worker who literally collapsed to the floor in the foetal position moaning after eating a mala hotpot which was, at best, medium heat.
Love the people, love the country, but Golden Curry's bright warning red "EXTRA HOT" is not bloody hot at all.