RR NDB:
Better expressing: Why not battery case has not a similar mechanism. Certainly would be safer a "venting" (rupture mechanism) than an explosion of a battery inside an EEbay. Electrolytes certainly would create a serious risk for a plane with this structure.
The description in the publicity video of the new design does indicate that the rupture plate of each cell will face a specially designed area (weak on details) in the blue box so that whatever comes out will not directly contribute to heating other cells in the battery. That sounds like a step forward.
The new outer box will then serve as the overall containment and exhaust system.