I should know because I wrote my thesis on it: shared conceptualizations and terminology are crucial in making sense of information from different sources (not the specific thesis, but the broad area I worked within). You cannot map them if you haven't got anything in common to map them together with. This blog was created in the hope of encouraging unity among Catholics and non-Catholic Christians (yes, because Catholics are Christians). This requires dialogue, and dialogue requires honesty, clarity, accuracy, and, to begin with, a common language. We all "talk Bible", but our doctrines can vary greatly. Add to that the fact that Catholics "talk Bible" in the light of Sacred Tradition, with the Magisterium providing the living voice of said Tradition. Even Protestants who believe in sola scriptura or "Scripture alone", without any Magisterium to refer to, can have wildly varying doctrines among themselves -- even when they use the same Bible translations!
So it is helpful when people like Mark Shea teaches us Catholics about "Evangelicalese 101", as an introduction to Evangelical thought and terminology. It doesn't cover everything -- that would probably work out as a huge volume or several volumes of books, but Mark makes a start and a point: we all need to be clearly heard and understood, and by acknowledging this for both sides, we can all hope to fulfill the will of the Lord that we may all be one as he and the Father are one.