"Haruna doesn't know what this practice is for anymore!" Don't worry, Haruna, I suspect the same thing happens to admirals all the time. "Well, we've scheduled the maneuvers, we might as well do them."

I think Katsuragi is doted on more by the Abyssals than anyone else but Zuikaku.

Also, i think this joint practice is to get Katsuragi integrated with the rest of the exile Abyssal fleet as their second carrier.