Here's the full lifecycle of a coordinated upgrade on the Cosmos Hub. There are actually two distinct eras — the old hard-fork style (cosmoshub-1→4) and the modern in-place style (cosmoshub-4 onward). Both are "coordinated upgrades" but work very differently.
Used when the SDK lacked an in-place upgrade module. The chain literally stops, exports state, and restarts as a new chain.