The process of making/drawing orienteering maps has changed completely in the last 25 years, but the recommended printing method for maps has stayed the same. However, the IOF has now updated the recommendations according to modern practices.
The IOF Map Commission have thus prepared an Appendix to ISOM 2017, which explains the background of the update, and the different printing techniques. You can read the full document here: ISOM 2017 Appendix 1 – CMYK Printing and Colour Definitions.