How does Jeppesen create its US charts?
FAA/NACO charts aren't masters, either

The master form of a FAA instrument approach procedure isn't the FAA/NACO approach plate for that procedure -- that plate is a derived document, just like the Jeppesen plate for that approach is.

The master, instead, is kept by the FAA in textual form as a set of Form 8260s. These provide a precise, formulaic description of any FAA approach procedure -- they're simply not in a form that's at all usable in the cockpit.

An example set of 8260s for the (rather special) KASE LOC/DME 15 approach can be found here.  Note that this contains exact records of fixes, governing obstacles, holds, and other procedure parts, as well as documentation about standards waivers and notes of changes.