If it is a "Certified" car at a Nissan dealership then they need to replace it with the same parts that it left the factory with as is shown in the Nissan parts diagram so the Off Road model needs to have the Bilstein shocks but they can be either from Nissan or Bilstein direct. If they are no longer available then they would need to negotiate that with you as an "equivalent replacement". Just like if you took it in for service for replacement shocks they should not be puting the base X shocks on an Off Road.
Just because you say I think it needs new shocks is part of the negotiation. If their mechanic doing the certification says they are fine then you don't have a base to demand new shocks.
Just because you say I think it needs new shocks is part of the negotiation. If their mechanic doing the certification says they are fine then you don't have a base to demand new shocks.