Bear with me, this is kind of what I'm working on right now, academically, so feel free to yell at me if I get lecture-y.
The misunderstandings are part of the point--it's a way of illustrating bilingualism and living in several cultures simultaneously, which leads to a) needing to explain yourself constantly to people who lack one or more of your cultural backgrounds, and b) being confused yourself, unable to "translate" things from your childhood to your adult life, for example. So by using that in their writing, these writers are playing around with understanding and meaning. They're actually not necessarily trying to explain everything; rather, they're experimenting with how much of a story you can tell when (some of) your readers don't understand everything. (Also, these works may not be written primarily for white readers.)
It's actually different from the Golden Age detective novels, where the use of French sometimes seems more of a way to show off an education. Dorothy Sayers, at least, tends to include translations. Also, Alvarez and similar writers don't tend to include whole Spanish passages--Giannina Braschi does, but her works are impossible to read if you don't know both English and Spanish, and she likes it that way.
no subject
The misunderstandings are part of the point--it's a way of illustrating bilingualism and living in several cultures simultaneously, which leads to a) needing to explain yourself constantly to people who lack one or more of your cultural backgrounds, and b) being confused yourself, unable to "translate" things from your childhood to your adult life, for example. So by using that in their writing, these writers are playing around with understanding and meaning. They're actually not necessarily trying to explain everything; rather, they're experimenting with how much of a story you can tell when (some of) your readers don't understand everything. (Also, these works may not be written primarily for white readers.)
It's actually different from the Golden Age detective novels, where the use of French sometimes seems more of a way to show off an education. Dorothy Sayers, at least, tends to include translations. Also, Alvarez and similar writers don't tend to include whole Spanish passages--Giannina Braschi does, but her works are impossible to read if you don't know both English and Spanish, and she likes it that way.