It's a bit of both, but they meant that it's an actual CarPlay screen: it supports "select" audio/video apps and the technical way it does that is essentially CarPlay-ing them off your iPhone.
edit: OK, some media outlets are saying Apple has told them "developers can bring over existing CarPlay apps", but there's no mention of it in anything Apple themselves have put out publicly which is why I was confused
> It doesn’t have an App Store. Instead, Apple has a curated selection of apps, including FaceTime, Messages, and Safari. A handful of third-party media apps like Spotify are available, and developers can bring over existing CarPlay apps.