It's really strange how some destroyers are mute, and others aren't...
He only has one hour to draw, so likely it is to ensure he makes the drawing in time. Probably the same reasoning goes to why only the main characters involved are colored, while the rest are not.
It could be like in Rugrats, in that the DDs can talk to other DDs no issue, but not to everyone else.
So yeahhhhh~We're hiding.This hereeeeeee~I think that's like the Enemyyyyyy?Found you...The Destroyers are in mid-withdrawal.Kancolle Manga "Yamagumo"! ①You seeeeeee~Hold uuuuuuuuup~Over hereeeeee~Heyyyy, everybodyyyyy~