The point of the ChromeOS dual-partition scheme is that ChromeOS system installs are read-only and immutable - they're the equivalent to creating a squashfs liv

The point of the ChromeOS dual-partition scheme is that ChromeOS system installs are read-only and immutable - they're the equivalent to creating a squashfs live system and burning it to a fresh CD, so it wouldn't make sense to de-duplicate data among them. If you don't care about this property and need more flexibility than that anyway (as with the average Linux distribution, which is updating stuff in /usr all the time), snapshots are the sensible choice and the dual-partition scheme is quite pointless.