There are a lot of things to say about the original implementation, and I think both of you are right in your respective theories and opinions. Some of it might have been a pure aesthetic question also: Hermitage and Oxford University with their multiple slots and theming bonuses would be too wide to get their own columns, whereas moving all the national wonders below the city (without adding something else) leaves a rather wide empty space on the right side of the culture overview, which they may have considered to look bad.