The World Magnetic Model (WMM) referenced in the article is usually updated every 5 years to meet its specified accuracy. This model is sponsored by the US and UK Defense departments and has requirements for accuracy, thus the unscheduled update when the magnetic field moved more than expected prior to the 5-year update.
The only advantage of the WMM (and the similar IGRF model) is that it is available at no cost. Most oilfield survey providers will be using a better global model such as the BGGM, HDGM, or MVHD. If there is a requirement for higher accuracy (less positional uncertainty) a local InField Referencing (IFR) model may be used. IFR type 1 models account for at least part of the local anomaly caused by magnetic minerals in the earth's crust. IFR type 2 adds to this a geomagnetic observatory to measure and correct for the disturbance field caused by solar flares.
IFR1 is commonly used in drilling long laterals in close proximity to each other, where a small angular error can result in spacing between wellbores that is less than ideal. IFR2 is most useful at higher latitudes, especially during geomagnetic storms. If you can see the Northern Lights, you probably should be using IFR2.