[nemothekid]

>What about reinstalls? What about developers/tinkerers who are probably flattening their devices on a regular basis?

IIRC Google gives you access to all that information in the Google Play dashboard, and for my apps, "reinstalls"/device upgrades were very rare.

[Karunamon]

Presumably that feature can only work if you redownload the app from the Play store. If you're restoring a backup or using any other method, it won't get counted.