Obviously it's a bug what are you even talking about. Naruto Online is not a game with passives / skills that have split effects for PvE and PvP modes.

In ninja talent description there is nothing about Jirayia mystery not working for PvE content so better think what you tell people because If it's not a bug then what, a scam translation from devs misleading people? If it's how it is then it should clearly say "it doesn't work for PvE modes" like any other half decent game does

It's clearly not Oasis fault that some game modes were made 5 years ago and new ninjas have bugs in those game modes but telling us that this is intended / fine / not a bug whatever is absurd.

I wonder what would you say if enemy units ignored mystery damage from paywall ninja, also "unfortunately this is not a bug, thats how it works in pve, sorry"? I don't think so.