Finally, the different "size" of the supply tanks and the 4kg difference between them means one engine shutting down before the other is designed as an un-missable clue that you really should be on the ground.
Isn't 4kg around 1.5 mins? Always assuming that the consumption of both engines in-flight were perfectly matched leaving the larger tank with 4kg. Sounds a bit odd to me. Surely they would have incorporated a distinct inviolate reserve tankage if that was the purpose?