The actual claim of this paper is that any watermark can be erased, which it justifies by proving the existence of an Erase function that removes the watermark without degrading quality. Therefore, since any watermark can be erased, let's use the simplest one that's visually identical.

This is true, of course, but also vacuous. The problem is that there is no sense of the computational complexity or difficulty of implementing the Erase function. The proof holds even if the watermark can only be removed in O(e^n) or some similarly absurd time span. A good watermark, like a good encryption scheme or a good password, is one that can be verified quickly but must be reversed slowly.

The paper's stance is no different from saying "since any watermark can be reversed, none of them matter, and we should just use THIS WAS WRITTEN BY CHATGPT".

Which is why you should never assume that a paper makes sense merely because it is technically correct.