Comment by Cthulhu_

Not necessarily, it can be done on-device, the screenshot hashed, and the results deduplicated and accumulated over time, then compressed and sent off in a neat package. It'd still be a huge amount of data when you add it all up, but not too different from the volume that e.g. web analytics produces.

Then server-side the hash is matched to a program or ad and the data accumulated and reduced even further before ending up in someone's analytics dashboard.