Okay, but it doesn't seem obvious to me why "detective story" necessarily implies "story about competition within a social class". If I read a blog post titled "20 rules for making pasta-based dishes", and one of the rules was "don't ever use cheese", I'm not going to argue that there aren't a wide variety of good dishes you could make without cheese, but I'd definitely walk away with the assumption that the author has some sort of bias if they think it's a universal rule.
To me a modern equivalent would be if Spielberg decided to make a reality show to try to do a good version of it: at the end of the day the genre is just shitty and unsalvageable for more reasons than one.
Also it is hard to figure out if the original source was prejudiced against Chinese people or not from this alone. This is a discussion about good and bad writing, not about race directly.
These stories are about members of the same group competing, not about in vs out-group competition.
i.e. imagine a school mystery: "the case of the stolen grade book" with culprit "random stranger who walked onto school grounds". The forbiddenness of such a solution is not racism/classism/ageism, but just that they're not part of the same social milieu of students, teachers, and parents. Them showing up makes all the fraught student<=>student, student<=>teacher interactions meaningless. Such a culprit's has different freedoms, social restrictions, and resources are different than the characters. If the culprit were another teacher with freedom to move, you get interesting contrast to students lack of mobility (needing hall passes to do their investigations). The mechanics of the story with an in-group culprit force readers to think about the social relations gaps they personally see in their own lives.
The political implications of this are inconclusive to me - it avoids "othering" traditionally outside groups (to the authors of these books) and portraying them as criminals - but it does this by ignoring their participation in society and making them vanish.
Culprit selection is difficult; compare Colombo, who has similar rules: "the culprit is nearly always from the upper class" - is this a racist/classist policy or not?