That's certainly credible evidence for past use I overlooked, though it remains unlikely to be useful with the advent of per-origin cache isolation.
The Last-Modified header can be used in exactly the same way, and isn't blocked by this extension, which harkens back to my original point: this is an extension that appears to see significant use by non-technical users, yet it breaks a browser feature by default. There are plenty of other methods of identifying a unique user that it doesn't prevent, so this seems like a pretty unexpected feature users should take note of.
The Last-Modified header can be used in exactly the same way, and isn't blocked by this extension, which harkens back to my original point: this is an extension that appears to see significant use by non-technical users, yet it breaks a browser feature by default. There are plenty of other methods of identifying a unique user that it doesn't prevent, so this seems like a pretty unexpected feature users should take note of.