Maps like 'Overlord' take the fiction a full step further, as they represent 'plausible alternate historic scenarios' - it's the Normandy landings, but not as we know them.
This of course stretches the history of World War II to breaking point, but that's ok - the gameplay possibilities on the map are fantastic, and that's what matters most in map building.
It will be no surprise then to see other maps to be completely fictional universes - the final step away from any pretense to show a historical fight in its historical surroundings.
The 'Glacier' map takes the cake in this respect, with its warship graveyard dominated by models of the legendary U.S. Midway and the German Bismarck ships covered in ice. In reality, these ships never met or were beached somewhere in a Nordic environment - it simply was a fun idea to pack a couple of World of Warships' 3D models in ice and have tanks drive over them.
These diversions from history are completely in line with what you wish for in an MMO.
Tankers want historically accurate placing of welds and camo on their tank, but this wouldn't mean a thing if the tank didn't also feel balanced in gameplay, fun to drive, and nice to dress up in new '3D styles' - (called 'skins' in most other games).
For maps it's the same: players couldn't care less about historicity when a map would feel unbalanced, favoring one of the two battling sides.
This is also the reason behind the creative and non-historical approach to many in-game events, like driving spherical tanks on the moon (in April Fools' events), engaging in tank races, or playing a little tank football in true Rocket League style, where you bounce a giant metal ball around a stadium while firing at opponents.
This is pure fantasy, of course. Which proves you can take an Massive Multiplayer Online out of the fantasy genre, like Kishlyi wanted, but you can't take the fantasy genre out of an MMO.