Of the Church, yes. Of the world, no. Wilberg was already the top selling
arranger at Oxford music before this song. When I was in high school choirs in Oregon in the late 80s and early 90s you couldn't go to ANY choral competition without hearing 2-3 Wilberg arrangements-- and none of them were this song, and most weren't sacred.
But you are 100% right that few in the Church knew anything about it. I was an active LDS kid, into choir, and knew who Wilberg was for years before ever having any idea he was LDS and worked for BYU.
Being self-taught is no disgrace; but being self-certified is another matter. Hugh W. Nibley