Others knew.  Obviously, "he" is the priest.  By facing the altar, as it was it the old Mass, he --- the priest --- can be interpreted by Protestants or know-nothings as saying "I am excluding you from what I am doing." Catholics who attended the old Mass, no.  As I said, it takes a pathologically self-oriented person to think that because the priest is facing the altar --- facing God, that is --- he is excluding the congregation.  Again, do you think the fellow in front of you with his back to you is excluding you?  Get over yourself.  You're not the star of the Mass.