Google is going to keep tweaking this because they have two conflicting goals. They want to cut off alternative app stores where they don't get their 30% cut, and they absolutely do not want to push people to other operating systems like graphene etc. They need it to be very high friction to accomplish the former, but if they make it too high-friction they'll trigger the latter. It's a catch-22, and they're going to dither in an infinite loop.