I know two people who love Pinterest.

Both use the mobile app exclusively & basically just use it for moodboarding/inspiration. They interact with it entirely within the app and don't leave the app.

Is it possible this engineer is working on a part of the product that doesn't directly touch the web publishing side and is (relatively) unaware of that side of the business.

I've definitely met engineers who don't dogfood and wouldn't be aware of aspects of their company's product since they haven't used it themselves.