I'm not a native speaker. The chapters are usually proofread/edited by a friend, but this takes a lot of time - we can't forget that, in number of words, this game is already bigger than the "The Lord of the Rings: The Two Towers" and "The Return of the King" put together.
So, I thought it was better to release this chapter as is now, and edit it in the next months instead of delaying it even more. Don't let the perfect be the enemy of the good and all that. But it'll get proofread, sooner or later. The previous chapters have also been released more or less like this.
That being said, it's funny that you picked an example that it's correct. Prophylactic moves are a thing in chess. Every professional commentator talks about prophylactic moves all the time. It's the correct term used in the field.