If a book on writing portable shell scripts across *nix platforms depends on commands not specified by POSIX, I don't think those books are doing their job very well.
POSIX.2 wasn't a standard until 1992. Perhaps it's the standard at fault for specifying the -E and -F flags rather than specifying the tools that existed in v7 in 1979. Authors and publishers didn't just pause for 13 years to wait and see.