You were talking about fortifications, not houses
The original term used was "fortified capital", which among other things requires both fortifications and houses. Certainly not the kind of settlement that you would expect of a nomadic people, although to give the author some benefit of the doubt it's possible that they're in the process of transitioning to a more settled society, or that they're more accurately described as semi-nomadic and travel seasonally between relatively established towns.
Tangentially, I wonder if the name Aishangior is a reference to Aisin Gioro, the name of the Manchu "barbarian" clan that defeated China's Ming dynasty and replaced it with the Qing. They were historically on the more sedentary side I believe, but I may well be stretching too far at this point. It's also difficult when the names are spelled differently almost every time they appear X'D