Forward retreats happen so much they're a running joke. You can actually abuse them to get a small fleet past a larger one pretty easily.

The biggest shock I ever got was specifically head hunting the last Timurid Khan, killing him, and not getting the faction eliminated screen. One of the defeated, retreated stacks off screen had gotten an auto-spawn general between turns. He had 4 chivalry and one of those 'noble in battle' or something traits. Hilarious.