If you look through the sysex manual, you'll see layer upon layer of pitch variables. They all interact in weird and wonderful ways. There's the master pitch (global), key shift and fine tune (per-patch), coarse and fine tuning (per-partial), the pitch envelope with LFO (per-partial)...
Then there's the key number given in the MIDI message, the pitch bend controller, velocity (which can influence the pitch envelope), etc. The effect of these can generally be adjusted per-partial, too.
Each PCM sample is recorded at a different rate, so that needs to be determined properly too (taken from the control ROM, but stored in a format that I'm not 100% sure I've worked out correctly).
Other variables not obviously related can also have an impact on the perceived pitch.
I've probably forgotten several things. Getting the pitch exactly right is certainly non-trivial, especially without digital samples.