You are not wrong, for all the ZED engines Nissan 'recommend' 98 (RON) premium unleaded and you should have a sticker on the fuel flap saying so and it is mentioned in the handbook. It also says that if it is not available:
"unleaded regular petrol with an octane rating of 91 (RON) or above may be temporarily used, but only under the following precautions:
Have the fuel tank filled only partially with unleaded regular petrol, and fill up with unleaded premium petrol as soon as possible and avoid full throttle driving and abrupt acceleration. However, for maximum vehicle performance and best driveability, the use of unleaded premium petrol is recommended. "
Its those last bits why I put in Tesco 99
I believe you will find the rating for Optimax is now 97 - it used to be 98. But as others have said, the the car will run fine on 95 as the ECU adjusts to changes in the fuel being drunk.