Heh, my brain goes similarly in fibre frustration. What are their clothes made of? Where are the animals for wool production or plants for cotton? Do they spin? Weave? Knit? Even a population as small as Dixing can't base clothes production around silkworms for silk either, so wtf.

(I have another show I love with an underground civilisation that I have similar woes for, but at least the majority of their clothes give the impression of being handwoven as opposed to mass produced in factories)