By dismissing Kwan's commentary (or parts of it) because he isn't a historical expert on early D&D, we are trying to prevent his criticism from being heard or seen as relevant and legitimate. Yes, gatekeeping. Only D&D super-nerds immersed in the esoterica of the game have any right to level complaints.
Kwan is reacting to the perfect storm of NWPs, the honor system, the Comeliness stat, orientalist language, and bad stereotypes as an Asian American gamer encountering Oriental Adventures.
To go all "well, actually . . ." after specific points like NWPs, honor, and Comeliness being developed in the pages of Dragon Magazine and/or appearing in Unearthed Arcana before being included in Oriental Adventures misses the point and tries to diminish his experience and offense.
It's certainly a fact that these three mechanical elements of the game were developed before the publication of Oriental Adventures and can be (and have been) applied to cultures other than Asian. It also is irrelevant to Kwan's experience reading through the book, it also doesn't change the highly problematic nature of the work.