Well i think the best thing to stop any abuse is to remove the portfolio assets. I can see how they can be helpful to show examples in files but if its such an issue for use it should just be the image assets. Its a case of one rule for one and another rule for another, and gets very frustrating.
Like parker and kent said the author quiz isn’t rocket science if someone wants the images and use them they will!
Simple solution to protect everyone is remove them! authors wont get caught out not knowing individual rules when downloading and using assets,”cause its not on the assets page, how hard is it to update this?” and then a total of 2 weeks to have a file reviewed because of it, and envato wont have to worry about people using there images of there portfolio!
Well personally i wont use them in a file again just because its trivial and has ruined my saturday!