Three different uses of the same power

Zano chose the integrity of a fixed supply over the survival of a month of history. Cronos chose recovery of user funds over an hour of settlement finality. Cosmos chose to move assets after the fact. The mechanisms differ. The fact they share is that a coordinated set of operators, exchanges and infrastructure providers can decide that a different history is the one that counts.

A chain is only as final as the willingness of the people who run it, list it and custody it to keep treating one history as canonical. If a small group can halt production, ship an upgrade and bring the venues with them, the network has practical reversibility, whatever the marketing says.