This was an issue in the previous read-throughs I've done from the 2e Historical series. The Rome book was similar, covering a complex history in a few pages. The Celtic book, too... Especially since it included a wide range of European tribal cultures, not just the typical ones people would expect from the term Celts....its also TIME.
Those two books had the relative luxury of a more leisurely view, I feel. I actually hadn't really considered comparing the 2e Historicals to Oriental Adventures before now: The Historical had the advantage of being explicitly supplements. I've mentioned before I feel like OA could act as an alternate Player's Handbook and it's mostly true, but the price is it spends a lot of page count on basic rules (stats, combat, spells, etc.) instead of building a setting. The Historicals didn't try to totally replace the classes (or provide alternate races) and accepted that "see the PHB" is acceptable for spells and such.
I do wonder if this was considered when the Historical were being developed. An interesting twist is the Historical are explicitly based around playing in the "real world" or a fantastic version thereof as the base, while Oriental Adventures is explicitly a fantasy world that sets its own history the same way other D&D material does.
I think it was suggested earlier that either Wa or Kozakura could represent different eras of Japanese history, as Shou Lung and T'u Lung may represent different eras of China... Although in both cases we have a sort of interesting set-up as there's a "Lawful" version and a "Chaotic" themed version of each, depending on which fits the PCs and the DM's tastes best. In my opinion, Wa comes off as a bit totalitarian in this brief write-up. although it's probably the better place to live.Shou Lung seems like it might be modeled roughly on something like T'ang or Song China, Wa and Kozakura, along with pretty much everyone's ideas of Japan even today, seem largely based on Tokugawa era Japan, with some later period social ideas thrown in.
That makes some sense from a cultural point of view... Less so from an economic point of view, in which there's usually some incentive to form a 'pyramid' with the most numerous social classes on the bottom. Do you think the Confucian order and the order here are intended as a sort of social order.. The closest analogy I can think of is a lot of Western philosophies at least consider the idea that humble peasants are important, even if they're not well-respected in practice.Actually, as I understand it the traditional Confucian theoretical social order was scholars/administrators>farmers>craftsmen>merchants, based on their perceived usefulness to society. Farmers rank above craftsmen because without the farmers the craftsmen starve, and merchants rank at the bottom because they don't actually produce anything.
This is a good idea to cover. I personally feel that architecture can help tell a lot about a culture, and it's quite literally "setting the stage." In this case, we're told to divide buildings into three types by social class: Simple commoner homes, palaces of the ruling class, and temples.
Peasant homes are wood or brick and with a simple floor plan, possibly a single room. There's a lot of "options" which, as AbdulAlhazred said, is at least partially because the section is covering a huge area with diverse needs for climate protection and such.
Noble houses are much larger and more ornate, unsurprisingly. A good tidbit for a DM to add is the attention paid to grounds around a noble's home, which might include extensive landscaping, fountains, ponds, and similar. Nobles can also afford walls for security and privacy.
Temples are important to the setting, based on the classes with ties to temples and related structures. Temples are noted as usually being a cluster of buildings in a walled compound, resting on a raised foundation.
A final 'class' of structure is military structures. This includes castles, watchtowers, and other structures. They're noted as being aesthetically different, but tactically similar to Western designs, built to make it difficult for attackers to get in.
I'm paraphrasing, but this is good information in my mind: Knowing little details to help describe a scene can add a lot to a DM's descriptions.