The 56 bits size is only available as a special accumulator register on the motorola dsp series they are using.. it makes sure no bits are lost during long calculations. After the calculation some bits will have to be striped away again to fit the result in a normal register.. which is 24 bits.
Contrast this to 32bit math on pc which uses 64bit or even 80 bit accumulators inside the cpu.. 56 is nothing to go wild about
on the samplerate:
44/48 is probably right for -some- parts of the synth, but it wouldnt surprise me if some parts (like the filters) are oversampled to 88/96 to keep the resonance stable at the high end.