But does it really do anything, or is it just snake oil?
I could be wrong on this, but I think for it to give any meaning full protection against fingerprinting you would need to use NoScript, like the Tor browser. But even if you disable JS, there is no protection against CCS fingerprinting, not unless you are willing to completely break rendering on most modern websites.
If all the browser start running custom JS limitations, you are going to have compatibility issues down the road. I don’t think anyone wants to go back to the time when you needed to write browser specific JavaScript.