There are literally many Kazen that don't even look alike! That's the stupidest argument.
It simply because is very out place compared to the rest of KGV class, attire and body proportion wise, mostly attire
I know there are ship classes that's like this like for example Alsace class having Flandre (Loli) and Alsace (Adult) in it, but at least they have something in common like matching theme on their attire (both having Holy-like being theme), but Anson design is very out place, it would be cool if she dress up similarly like the rest of KGV (personally, I don't really care if she's a loli or not), but she's dressed up like those ship girls in submarine class, like is she a submarine or battleship???
I'm having a strong suspicion that the artist who design her mistaken it for HMS Anson of Astute class Nuclear Powered Submarine, and when near deadline the artist just realize the mistake and decide to build a battleship rigging around her
The most popular theory is that the art was meant to be for the HMS Sunfish, a Royal Navy submarine from WWII. Her resemblance to Cherino from Blue Archive is probably a nod to how the real-life Sunfish was given to the Soviet Union in 1944.
It wouldn't be the first time Manjuu used art that was meant to be for one ship and give it the name of another ship, like HMS "Manchester", who was clearly supposed to be HMS Emerald.