Lyman:
Your car battery has six cells. It is a battery, unto itself.
The blue box in the Boeing contains eight three cell batteries, in series.
If you look inside a lead-acid battery, you find that there are often multiple positive and negative plates, with individual separators, layered inside a single electrolyte-containing envelope constituting one cell. The same appears to apply to the Boeing "cells", although the physical separation of the sets of electrodes is admittedly a lot greater.
So, I am willing to consider that some aspects of the cell can be interpreted more easily by thinking of them as three unit cells in parallel, I am not willing to go all the way and say that they should be categorized that way.
I will accept the description of the blue box as a battery bank rather than a battery because it does have individually removable components.