More speculation: The reason the module can fit up to 25 groups (instead of 24) is that all modules contain 25 groups, but one is a spare, and not in the 96s loop. Assuming there is no way to remove or insert a group of cells, when one cell goes bad, the group is bypassed (or shunted after discharged) and the spare group in the module (or in another module) is spliced in to maintain the 96s configuration.
75 kWh / 4416 = 17 Wh/cell or 4.6 Ah. Add 6% for the unused buffer and you get 18 Wh/cell or 4.85 Ah.
75 kWh / 4416 = 17 Wh/cell or 4.6 Ah. Add 6% for the unused buffer and you get 18 Wh/cell or 4.85 Ah.