Yes, no other restaurants or pretty much anything else was open on Christmas. Sunday nights at Chinese restaurants likewise became a “tradition.” Jews who cared a bit more about the Torah dietary laws would order vegetable dishes. Vegetable subgum chow mein and was a popular “starter” dish for Jews. Over the years, Sunday nights became a common choice. Only a handful of cities had kosher restaurants in those days. Later there were even upscale, strictly kosher Chinese restaurants, like Moshe Peiking in Manhattan. The kosher ones often used bilingual Hebrew/English puns for the restaurant names.
For the record, there was Jewish migration and communities who kept their Jewish practices in China way back at least to the early 1st century B.C.C. There are still Jews in China. Jews were honored citizens. In some areas, like the South of China, schools and government offices closed on Jewish holy days.
That should have read, “B.C.E.” (aka, A.D).
Interesting!