It's not easy to make things stay waterproof after such an event. Water will find a way. The simplest thing will likely be the Achilles heel of such thoughtful engineering.
It doesn't mean that should stay there, as-is, forever. Like most failover solutions, it gives you a bit of time during an incident to come with a proper solution for the future.
Having it not fully waterproof (and maybe they also took that into account) has probably been seen as an improvement over totally crushed by rocks and bricks.