Is it coincidence, that this weapon arrangement resembles that of her dream in Ido's post #3283803?

After looking at other entrances to this pool: Yes it is! Or better: this arrangement seems to be canon for Kiyoshimo's battleship dreams.

It's Yamato's rigging, so of course it'll look the same.

Remember that Kiyoshimo is a battleship maniac and Musashi fangirl. Also remember that Musashi has the same rigging as Yamato.