I can easily protect myself from GA tracking.

You can't compare a mobile app with a web application. One of the author's points was that "view source" world as we know it in the web doesn't work anymore on mobile apps. That's why he had to resort to Fiddler to see what is going on under the hood.

The better question is: What's the difference between this and a desktop application that gathers your data?

If the same thing happened with a desktop app (spying on your every click, "calling home"), it was labeled as spyware within days.

Analytic of every click on a site is by no means better than these, and many apps didn't specify such behavior in their Privacy statement.