The battery system is just like all of the other pieces of this aircraft that were designed to the micron, without any regard to constructability and general realistic materiels tolerances.
Remember the delamination due to the carbon fiber shims being "out of tolerance" to design specs, by microns?
it is also interesting to note that Boeing designs and tests the components individually, such as a single wing assembly, while Airbus tests entire wing/fuselage assembly, not only in design, but in aerodynamic modelling and destructive testing...