That's the picture I get too, but I don't see how clearing the cache doesn't, you know, clear the cache. It would seem to imply that if the Etag is still around, it's not really cleared - maybe the data is gone, but the knowledge that the data existed isn't. And it persists through privacy-mode.

Which means I/we am/are either misunderstanding something, or the people who designed privacy and cache-clearing tools had a massive blind-spot.