WhatsApp does monitor their network and API calls being performed. This way they ban spammers and fake clients going on the WhatsApp network. I suspect they use some form of Machine learning to filter out the non-users and when you're identified: you're getting banned. This means that you can no longer use your phone number and need a new SIM. So this story isn't feasable for "huge amounts of data". You might be able to download a few 100k of profile picutures but you will get banned.