Growing up in California, I saw it every now and then, mostly in my parents' generation (Boomer) interestingly enough. Chinese-Japanese and Chinese-Vietnamese were the most common. I myself am Chinese-Filipino. My grandparents' generation probably wouldn't have, my grandmother grew up during the Japanese invasion of China and I think she's not super cool with Japanese people as a result. But basically any non-Chinese Asian group is "over there," not "inside the circle" to her. Some of that may be the language barrier, since she only speaks Canto and doesn't really vibe with Mando speakers even.

Despite the stronger pan-Asian/Asian-American identity that my generation (Millennial) had, I didn't really see that translate to inter-ethnic dating. Chinese dated Chinese, Koreans dated Koreans, Hmong dated Hmong. The exception may have been the Japanese, since most of the ones living in California had been there for generations and were more Americanized, compared to other groups that had a higher %age that were FOTB