I call it cutting away because every sane phone manufacturer includes those services into their devices. I think android phones running AOSP are not completely usable, at least for me. AOSP is missing critical components, like I mentioned before. A central push infrastructure is essential for me. Google is just splitting their Services so that they can get manufacturers to pay for licensing, but not because they think AOSP is fully usable on it's own.
But this seems like a discussion that will never end, so I will conclude: the bunq app is currently using more Google components than just the Play Store, so I don't think they will be able to publish the app directly in the near future.
