There is no ‘standard’ offset for inset doors. Most hinge manufacturers simply state that you add the door thickness (which is often 18-19mm, but varies) to the 37mm, to cover all door thicknesses.
You need to look at system32 as group of separate standards, and only use the bits that are appropriate to your build (and be prepared to ditch the bits that aren’t). Broadly, there is the vertical spacing and the horizontal spacing. Vertical spacing should be used where you need flexibility to move hardware, or where you are buying in door/drawer fronts which have heights that are designed to fit in with system32. Horizontal spacing should be used if your drawer runners require it. Horizontal offset should be tailored to your drawer runners and to how you want your drawers to sit in the carcass.
For example, Blum drawer boxes expect a 37mm front offset, and have holes in groups of three, so you can use them as internal drawers simply by using the front hole, or standard drawers by using the rear hole of the three. But another manufacturer might not have this flexibility, so you would need to offset your holes accordingly if you wanted to turn them into internal drawers.
I suspect the recommended sys-az offset is simply a function of the runner design, and the fact that Festool want the drawer fronts recessed slightly to avoid any risk of snagging. They are not expecting anyone to fit hinges to these cabinets, so don’t need to worry about that when choosing their offset.