That would be the core of the structure, but the entire facade (the only bit visible ingame) is thoroughly neo-gothic with all the typical features.It's considered late gothic, if I'm not mistaken.
The generic flying buttresses, those copy-pasted spires, etc. You can see a great example of how this works in Barcelona, where the OG gothic cathedral got overbuilt in a neo-gothic style and added the same sort of features to everything.
Of course Civ is a game that has no idea about architecture or its own passage of time (I mean, stone age Washington should be a decent hint, right?
) but since you're clearly at least somewhat interested in these buildings, I thought it might be a fun note/headscratcher for you. Same thing for other wonders you have there, though haven't commented on. St. Vitek cathedral's half was not built until 1800s and... you guessed it, in neo-gothic style. Koutoku-in was housed in a building like its older brother in Nara (Toudaiji, itself a building that went through 3 different iterations) like so, etc.