We've agreed too much lately, so I'm happy we can finally disagree on something.

You're applying blanket privacy logic while ignoring the context of Spotify's (and other app devs) issues. This has nothing to do with, and is nothing like that, incorrect btw, claim of Google selling data.
This is about having the ability to improve services for customers who chose to use the devs apps. If devs have no visibility to their customers, then they're guessing at what's right, what's wrong, and what needs to change. What dev doesn't need to know about customer churn? What dev wouldn't want to show appreciation to loyal customers? Myriad other reasons why knowledge your customer base is essential to staying relevant and actually making money. Make no mistake, when you choose to purchase an app you are that dev's customer as well. Would you not want their products to improve? Hyperbolic --> Nobody wants the App Store to get as bad as MAS. Besides, this isn't a binary situation like: Gimme all the informations or gimme none of the information. Allowing devs to improve their offerings benefits all concerned: Apple, the dev, and most importantly, the customer.
To use privacy as some type of clarion call against information sharing is short sighted in my opinion. None of companies like Google, Facebook, Apple, or Spotify sell customer data. I wish people would stop with this. They all collect customer data to, according to every single one of their privacy policies, help improve their products, services, and advertising; among other things.