Then you need to read the GDPR law, which I have and had to pour through long documents compiled by expensive law-firms to grasp just how huge the requirements were. It very clearly states that a service must give you a method that allows you to download and delete all your personal data. That can be as simple as having a contact email with a human downloading your data for you from the database directly or highly automated like Facebook does, but the feature absolutely has to be there! Spotify went for the automated version of generating that data, so now they should legally be bound to satisfy the requirement. The API is already there, has been for ages, but Spotify now claims the transfer apps are not using it the way it was intended.
Yep, this is why Google allowed you to download everything tied to your account, even all your YouTube videos, comments and history.