Black authors necessarily multilingual?

This is the abstract of an article entitled "Expanding 'South Africanness':  Debut Novels" (2009) by Margaret Lenta:

"In this article I examine a selection of debut novels published in South Africa in the period 1999 – 2008 in order to determine what inspired the authors to embark on the writing of prose fiction. A large number of such novels have been produced in this period, and most of them demonstrate the new freedom that authors feel to deal with subjects disapproved of or banned under apartheid. I have based my selection on the categories 'giving voice to previously silent communities'; 'sex and gender'; 'mixing languages', a phenomenon now characteristic of novels by black authors; 'writing back', that is, responding to and taking issue with earlier works; 'the roman à thèse', implying that the work becomes fictionalised argument. The final element is 'fusion', by which I mean that the novels register that people of different ethnic communities are now free to know each other outside of their work, and to form what ties they wish."


I wonder if it is true that mixing languages in a single work is now "characteristic of novels by black authors"?  That would make multilingual novels mainstream, wouldn't it?