It is the standard used in the F7s. Articles are copied and pasted there for counting. No interpretations or vagaries, it is just the Official Word Counter.
Before the OWC, there was no standard and players used MS Word, or some other online word counter. In some cases, players physically counted the words.
Clearly this was open to conflict as different methods brought up different counts. The OWC solved this problem.
If you paste the finished article in the OWC, then you can't go wrong. Just make sure you are pasting the article as the ref will see it (from headline to final word).
If there are too many words because of an errant space issue, then cover it by losing the word(s). I did it myself this this week - an extra word popped up in the finished article, and I did a quick edit before fulltime.