The same problem exists for the MKL27Z4, the archive only contains fsl_clock under devices/MKL27Z4/drivers but no other files.
btw, why is there an MKL43Z4 folder at all, if I 'build' the sdk for the MKL27Z4? of course they are similar and AFAIK the suggested dev board for the kl27z is the frdm-kl43z but then an option 'support recommended dev kit' would make sense...