No offense, but you didn't really resolve the issue in the other linked thread, and you haven't really resolved this one. You have simply repeated the issue back to us.
This is not resolved.
This simply isn't a Dropbox problem. The Camera Uploads feature is meant to upload any new photos or videos it finds in the DCIM folder (Camera Roll on iPhone, Gallery on Android, etc.). Dropbox can't distinguish between the different apps that may be dropping images into that location. It simply sees an image and uploads it, as it's supposed to.
If you want to prevent that from happening, disable the option within WhatsApp to automatically save files to your phone. Or, disable the Camera Uploads feature in Dropbox and upload your photos and videos manually within the Dropbox app.