I think expressions like “on the altar” are regionalisms. That expression is quite common around here to refer to being in the sanctuary, whether as a server or a reader or an EMHC. It can lead to some serious misunderstandings, particularly if care is not taken to use proper terminology.
A college student was asked to read when she was home on her Christmas break. As she was doing the first reading it was her job to bring the Book of Gospels up in the entrance procession. I told he to put it on the altar.
She repeated, “On the altar?”
“Yes, on the altar. Father will get it from the altar when it’s time to read the Gospel.”
So, she went up in procession and proceeded to put the Book of Gospels on the floor in front of the altar. Because to her the sanctuary was “the altar” and the altar was “the table.” “But Mom,” she explained to her mother, “you always told us we had to behave perfectly when we were “on the altar”. Can you see how I would make that mistake??”