Why the Japanese formation really was a scratch force

Was the Japanese formation essentially a scratch force thrown together for the operation?

Yes. Its mixed ships and commanders had little time to work together, unlike non-homogeneous Allied formations that were normally reinforced and trained before combat.

The Japanese ships had been thrown together as a scratch force. A mixed formation was not automatically ineffective; British destroyer groups also absorbed ships from different classes. The difference was that Allied reinforcements were normally attached to established formations and given time to work up together. At Empress Augusta Bay, ships and commanders with different characteristics entered combat after only hours of coordination. The comparison makes infrastructure, training time, and force integration more important than visual uniformity alone.