So by your definition, are "biang", "kiang" and "duang" valid pinyin, considering those are pronounceable and understandable to millions of people, though they don't appear in your table?
I know that biang is the name of a particular noodle; I'm not aware of kiang; and I believe that duang is a sound Jackie Chan made once. Which leads into a tangential question -- "duang" has no meaning. What would it mean to say it is "understandable" to millions of people?
[1] http://finance.eastmoney.com/a/202107151999911843.html [2] https://www.marieclaire.com.tw/lifestyle/art/58762