That really doesn't answer the question. Munchberry claims these analytics tools have cross domain tracking and I'm asking how, precisely. In part because of professional interest, and in part because I don't actually think it's true.
You specifically got one detail wrong: it's not just for analytics tools. It's the adtech industry in general using this technique, and Adobe offers its analytics as part of its marketing software suite.
From their own site: "What is Adobe Experience Cloud? It's a collection of best-in-class solutions for marketing, analytics, advertising, and commerce."
You're right, Adobe Experience Cloud doesn't sell information, so how problematic you find the product depends on where you draw the line on privacy.
Specifically, Adobe Experience Cloud definitely offers retargeting capabilities (ads following you around the internet) and the ability to get statistics on the effectiveness of that advertising. If they're at parity with competing marketing suites, then they also have attribution capabilities to track you with per-user, per-interaction granularity.
A site that serves Adobe Experience Cloud cookies in the third-party-disguised-as-first-party way is likely enabling this capability for all marketers that are going through Adobe Experience Cloud. So the interesting question would be whether you, a visitor to Fox.com, consider being watched by marketers who aren't Fox.com to be a privacy problem.
All of the above is more private than eg google analytics because of the lack of cross domain tracking... I'd consider it a big improvement vis-a-vis google's product suite.