While a player's death animation is playing, they can still see updates around then (blocks changing, entities moving, etc.). After the animation is over, no updates are visible anymore. I assume this means that no chunk updates are being sent to the client.

If the chunks around the dead player are not loaded by other means, they invisibly unload after 1 second (after the death animation). This is likely intended, to stop items from despawning when dying while AFK.