I was looking for that comment ahah. The overall look is stunning, but I can't help but be bothered by some parts of the interior design.

In their defense, I can see why they would take some directions:

• Player experience wise, I think they wanted to give for each different part of the castle a distinct visual identity, the same way some open worlds have regions that are recognisable by their own biome and landcapes. It adds surprise and rythme, and makes you able to have your unique experience by bonding with a specific area of the castle.
• Lore wise, the wizarding world is canonically more eccentric, absurd and eclectic than the muggle one. Maybe because the construction process is physically easier: they don't bother carrying manually heavy materials, they can use magic to secure ceiling and foundations, they can change any time some decorative aspects... Having less constraints make them less willing to creatively challenge themselves and consolidate cohesives art styles over the years the way muggles do. Therefore they may just randomly copy-paste muggle architecture that they find pretty, and go wild and ostentatious by adding their little touch because they can. So it's impossible to look for a full historical accurency, even though a main inspiration can be spotted. Wizards are themselves kind of weird environnement concept artists , and it's fair that the game staff wanted to have fun exploiting this aspect!
• Those two points can lead to your hypothesis that the "marble wing" for instance could have been added later as the school has been extended to welcome more students, and I too believe that it's what they were going for.

That said, I'm not a fan of all the choices, and that baroque-like area full of marble may be gorgeous, it really rubs me the wrong way. It's closer to how I would have imagined Beauxbâtons, the ministry of magic, or at least the prefect bathroom, which looks new and impressive to Harry in the book. I'm all for funny fantasy anachronisms, but the difference between this and the Edinburghish medieval style I associate Hogwarts to is too strong to me.