Here we report bugs in the beta.
It is a good point, that I am aware of. As mentioned in the first post, these are stats from a 6% roll-out. The opt-in beta resulted in less than 200 installs, these stats are from ~3000 randomly selected users, both existing and new installs from play store. The stats are collected from a couple weeks after end of beta, start of roll-out so that most of those 200 people stopped finishing new levels (I measured this before starting collection).