What's happening here? A destroyer ambush?

uhh... probably... but its more likely its in game mechanics if you upgrade your dock AKA "bath house" you can repair more ship daughters surely they will appreciate your hard earned money... or thats what we like to think

YEah, you can say that. The bigger one will make more place to repair your ships. At least you don't have to stress waiting for hour ;D

After I started playing KanColle, I can now truly appreciate this Admiral's gesture as well.