Yes, 19khz is the pilot tone. But the stereo signal is modulated so that there is no carrier at 38Khz, so the 19Khz is used to regenerate the carrier for demodulation.
To be a little clearer: the R+L signal is combined with a R-L signal that has been suppressed carrier amplitude modulated at 38Khz and these signals then frequency modulate the transmitted signal. The receiver can't demodulate the R-L signal without a reference frequency so, for reasons I have forgotten, it is sent as a 19Khz pilot tone.