I can only assume that the values of 30 pf for quartz and 47 pf for ceramic at f<25 MHz must provide for the desired fo as set by the crystal, whether 11.0592, 12, or 4 MHz.
Thedy do.
The oscillator inside the '51 is not tuned by any means, thus it will run at the fundamental frequency of whatever crystal you choose even if it is 32.whatever kHz (the clock crystal).

Erik