Not only did Kernighan and Ritchie not update the C book for a standard newer than C89, Kernighan underscored that by updating the The Awk Book in 2023 (with Aho and Weinberger: the other two letters in Awk). As if to say C is so far gone that even Awk is more worth writing about.
KNR have written a lot of books that they have not updated over the years.