To digress into the real world, Oblivion was made by a different team with very different ideas than MW's. Something as nitpicky as consistency in architecture from previous games was probably overlooked completely. I don't see any "Hlaalu" influences in Cheydinhall. It looks more like something a slightly gothed-up Tinkerbell would live in.

Haha, in a word: yes.

It all falls into place now.

There are a couple. First, the tendency towards rectangular and modular shapes creates a flow of buildings so that as you peer down a street, you can't quite tell where one street ends and another begins. Combine those streets and a few spread open plazas and you have the feeling of a claustrophobic city with breathing space at key areas.
Speaking purely on an architectural level and not on the effect on the viewer though, aside from the rectangular shape (as any building with any sense of efficiency about it will do the same), the consistent figuring on the windows and their shape is reminiscent of the bug windows of Hlaalu. Finally, the second floor of both architectures are a lot more ornamental than the first floor (where people on the street are apt to look).

Also, you have to do some extrapolating. The cities and towns in the Velothi mountains are not going to be the same as Balmora. Cheydinhal will mirror those near it. Also, it may have a scooch of Akaviri influence now that I'm really thinking about it.