Most cameras already produce metadata. You can remove this metadata. Can you not also detect and remove watermarks?

The paper references some threat models they considered. They suggest someone might "possess paired information (both original and watermarked content)" and therefore be able to undo watermarking. Presumably it's fairly easy to get identity operations out of image APIs that would result in this situation. I'm not sure that addresses echelon's main concerns though.

The metadata is kept separately from the original data, and is, by design, modifiable and removable.

Watermark, by design, irreversibly modifies the original data, and is, by design, hard to remove without producing detectable artifacts (or rendering the data useless altogether).

In short, the answer is no.