A cashew is a cashew no matter what. But a pine nut is not a pine nut. This was back when pesto was one of the biggest sous-trends ever, and everybody was eating it. Pine nuts are still considered gourmet, but the trend is over. Both Grimo and Brown suggest sampling a nut before buying, or at least checking the color.
Pine nuts turn rancid quickly because of the high fat content and keep best in airtight storage.
No, those pine-scented car air fresheners don't count. Odds are they probably wouldn't do much for your pesto, either.