Source?

If this is happening it would be easy to detect by the upload bandwidth spiking during AR mode.

The 3D scan mode is a specific feature you have to use in the app that uploads 100s of megabytes afterward. It advises you to go on WiFi to do it.

If the AR mode was secretly uploading images that would be a scandal in itself.

I don’t think people who play a lot use the AR mode when catching Pokémon. It’s easier without it, and saves some battery. But I could be mistaken.