Had an old boss who was a Romance languages PhD dropout. He told me that Borges' first language was English (his father was half-English and it was the primary language at home), he went to boarding school in Switzerland, so he basically doesn't write Spanish as a native speaker. This can make his writing in Spanish more accessible to English speakers, but jarring and dissonant to native Spanish speakers.

Can't judge the merits of it myself, but it seems plausible.