Thank You So Much for Your Reply. However:
1) In reality, although I am Not a Chinese but I have eaten Wonton Noodle Soups (including Char Siu Wonton Noodle Soup) sold from many Chinese Street Noodle Carts throughout Saigon (including those in Cholon area where many Chinese immigrants and their descendants live) since I was a high school student in the mid-1960s until the late 1990s when I immigrated to the US. Most of the Chinese Noodle Soup Sellers do speak Cantonese as their mother tongue instead oc Mandarin as people in Beijing. Of course in their Chinese noodle soups sold to customers in Saigon often include chopped green onion but Garlic Chive is also a frequent/usual ingredient of the Soup (the English web page of Wikipedia also stated that Garlic Chive is also often used in Guangzhou and Hongkong-style Wonton Noodle Soup). So I do Not think that Garlic Chive is only used as an official ingredient for foods in Northern China. In Saigon, Garlic Chive is even used more often in Chinese Street Noodle Soups than Bok Choy (小白菜) or Choy Sum (菜心) as added vegetable for Wonton Noodle Soup.
2) Also existing in each bowl of sold Wonton Noodle Soup in Saigon is a small DEEP-FRIED SHRIMP CAKE of round-and-thin shape.
3) But SIMILAR to what You described in Your Recipe, the (Char Siu) Wonton Noodle Soup sold d in Saigon also often uses the Hongkong-style thin egg-and-wheat noodle that has been mixed withye water (枧水) during the production process, making this kind of noodle having a chewy texture and special taste which I like very much. I feel quite regretted when Not every Chinese Supermarket in the US frequently sells this special kind of lye-water egg noodle (碱面／碱麵). But again, THANKS A LOT for spending time compiling your (Char Siu) Wonton Noodle Soup articles with illustrated video clips enclosed

It’s very interesting that you find so many versions that have garlic chive. We usually add it in noodle soup in Northern China, but not often in this recipe because it’s a Southern Chinese recipe. I definitely think it’s optional for this one. Sliced green onion and fried shallots will work well in this one instead of the garlic chive.