That wasn't entirely my point, however. The training set was only a part of the problem, which in its totality was that the developers failed to consider that the functioning of their system could be affected by the biases they didn't even know they had, in this case of being more likely to see light-skinned faces as belonging to a human.

Their failure was not just in lacking diverse training sets, but diverse QA, or at least QA looking for those blindspots which eventually became evident.

So, correct, it's not as simple as having "sufficient" data.