>That’s because, while Google expected apps to use Google’s own billing system for purchasing digital goods, it rarely actually enforced the expectation
>The billing system crackdown
>Starting June 1st, Google said it would remove apps that didn’t comply with its billing system rules.
>Oddly, in March, Google announced a pilot program to let app developers use their own billing systems. The pilot program includes Spotify but not Amazon.
The article says its the billing system, and mentions it multiple times. I'm not reading any court documents, as I am not a legal scholar to offer an opinion on them. I would invite you to write your own analysis, and I'm sure there will be people who would be interested in your scholarship.