You are giving Oasis way too much credit by assuming they can change a skill even if they wanted to.

You have to understand that publisher only implements what developers give them. If there is such a difference between Tobirama in NA and China then there is about 95% chance that's how Tobirama was first implemented with the breakthrough, and then due to people complaining the skill got buffed. There is also remaining 5% chance, that developers wanted such a change, which is rare but happens.

Unless of course that is just a mismatched translation line, such things happens too.