I've never had good luck harvesting seed on Chinese Iris species, or even the North American woodland Iris such as Iris cristata. It helps being retired (wish I was) or unemployed (wish I wasn't, sort of), because I get to observe in much more timely detail, about what plants are up to. Year after year, I see big, fat, 3-sided pods on species like I. koreana and I. odaesanensis, two wonderful Chinese woodland Iris species, but rarely ever get any seed, although do find seedlings of I. odaesanensis often enough.
So, I discovered that the seed pods are much like other ephemeral seeders such as Jeffersonia, Epimedium, and Corydalis, they are actually ripe and mature when they're still green, when they are "al dente" and not "fully cooked", but even moreso with I. koreana. Harvesting the large seed pods while green (noticing that a few had gone over to yellow, but with nothing inside), and snapping the green pods in two, there's good seed in there, like golden kernels of corn with starchy appendages (elaiosomes) that are attractive to ants.
So, I harvested seed on Iris koreana, odaesanensis, and henryi much earlier that I would normally, and found a good percentage of viable looking seed. Time will tell whether my early seed sowing efforts are the proper recipe for success. I checked some green pods on Iris cristata today, and while the green pods had developing fleshy seed inside, it was too early for them... but I shall keep checking.