I explicitly talked about block level and your example only makes sense with unencrypted data, wich I wasn't talking about. After that it's plain science. Explain, how - in encrypted data! - bit patterns are more likely to occour in a block than other bit patterns, and you're on with deduping. If you can't, you're not, because addressing is the copy will be at least as costly (in terms of space needed) as the real data. It's just maths, arguing won't help you there.