The map's architecture

[Bridge]

It didn't bother me the first time I played through, but now for some reason I stopped to think about how illogical some maps are set up.
Some are fine, such as back hall, main entrance, cistern, wine cellar, guest room and the archives.
Some make less sense (especially the chasing scenes). You run through long corridors with inexplicable turns and T-junctions that don't have any logical reason for being there because there is no room there.
Some make a little sense but are still a little strange, such as the prison cells, rainy hall, old archives, where you have long corridors and a few cells and rooms, but also a lot of inexplicable voids, the whole thing just seems to be more of a tunnel system than a 'block', which seems like a very inefficient way to design a building.

Also I wonder, if you could stick all the maps together, attaching them where they should be attached (the level doors), assuming the engine theoretically supported it, would the maps fit together, or would there be overlapping sections?

It actually is explained that Alexander uses these underground tunnels for getting around the castle (at least the sewers, but I think the Archive Tunnels are technically the same type of structure, just adapted for travel by Alexander). As you know, sewers in real life are only used by maintenance people and actually do have a lot of dead ends that have nothing but machinery, which would explain the illogical architecture (as it wasn't designed to be a part of the overall structure). It is not a hand wave to say that Alexander did it himself because there is a flashback where he talks about making some heavy modifications to the castle, reinforcing old structures, which would no doubt require the use of these shortcuts.

On top of that, the omnipresent Shadow often causes things to shake violently, which would undoubtedly cause the weaker parts of the castle to cave in, which would explain many of the dead ends.

EDIT: Actually, I got the impression that everything underground was commissioned by Alexander. Personal elevators were definitely not common at that time and it was probably a huge headache to get working and because the castle was not originally designed to be underground (assuming Alexander was not the first owner) then that would make all of these structures custom built. Though he did mention one of his duties as baron was also that of a prison warden, my guess is the authorities never actually inspected the prison cells and thus were not aware of their actual location, which could mean he originally had a dungeon but then built a new one underground. If my theory is correct, that would mean all of his servants built the underground sections to fit in with the sewer and cistern systems over the course of decades or centuries. If you go with this theory, actually all of the illogicality of the underground sections is justified, because he is crazy. That netherworld looking thing (Chancel) and the Choir especially are definitely customized.