Rat,
As far as I am aware, Jepp does calculate the information. From errors noted from posts on this board, Jepp has recalculated and revised several plates.
In the procedure design world, we must validate the coding of the procedures and waypoints on the AIRAC cycle, and there are always waypoints and runways ends that are incorrect. Curved fligthpaths are always a negotiation.
In addition, there is quite a bit of the world where the AIP is not standardized to the standard datum. Jepp has to do the conversions for these datums.