adwcta
King
I don't follow. Are sea trade routes supposed to help Japan somehow?
Ships don't heal outside of friendly territory. Especially early on, when open borders is not established yet, and you're working with your triremes, the Japanese UA (which has always shined more for naval/air battles than land battles) will be more useful. I'm confident it will be a noticeable difference between Sailing and Compass (which a large and important chunk of time in the game).
Ottoman (and actually Byzantine too) will get a boost for similar reasons.
I mean, it's still not great, but barbarian ships are nasty to triremes on higher difficulty levels if you don't have Honor.