How does that even happen? like getting word for word defog descriptions?Between 5th and 6th gen I helped Serebii write a couple articles on his site. Basically I'll just say that he does a ridiculous amount of work to get all that info up as quickly as possible. Mistakes happen, but if you message him he's usually very quick in fixing issues. Early in a new gen or game he's more concerned about getting as much info as quickly as possible though even if a few errors occur. He's getting millions of page hits right now, it just makes sense financially to focus on him getting all the info up with 99% accuracy.
But if you're looking for the exact game mechanics from a competitive standpoint, you're best off asking on research threads on Smogon and, like 6 months from now, Bulbapedia. Probably Showdown will be very accurate within a few weeks. But as far as research on stuff like this we're better off doing it ourselves.