The Nissan 350z requires 91 octane premium and it is recommended in the other Nissan cars that use the 3.5L V6. But for the 4cyl. cars, only 87 is required (except SE-R). So I think your guess about just using one pump for all vehicles as a matter of convenience is probably right. But the manual shows 87 AKI...that's all you need.

By the way...a sales manager or a technical manager?

About Canada using RON...thanks for correcting that. I've not seen RON method used anywhere in US...maybe just Europe & Asia now?