why doesn't the Japanese version get protection?
Engine update. While i'm by no mean a programmer, you can see the pattern that, before the JP update their engine, it's incredibly hard to mod it, and even if you do find it, it's placed in VIP section. And after the JP change their engine to Unity 2018, I can only assume that the protection is likely still there, just barely. Because back then, you can't play the game in rooted device, but now you can. The only annoying thing is that I can't clone the apk anymore.