Let's just make Shigure as an example for a clearer explaination.
This is Shigure in 1939. The photo is quite fuzzy, but you can still find her rear single-mount turret.
This is what her looks like in 1944 in battle of Leyte Gulf. As you can see, the single-mount turret had been replaced by a flak platform.
Another Shiratsuyu-class destroyer, Harusame. That's what I'm saying: all the Shiratsuyu-class destroyers have that turret in early war period.
Harusame in 1944. As you can see the turret had been removed.
Let me give some other examples. As I mentioned before, the Kagero-class also underwent that modification.
The IJN Yukikaze, the most famous one of the class. This is her looks in early war.
That's Yukikaze after the modification. Just remove the second aft turret same as Shiratsuyus and Hatsuharus!
