A Ladder-Mate Question

OK, I think I understand. The Queen, because it also moves diagonally, will always protect the Rook from being captured, but the Rook can't do the same for the Queen? Right?
It seems unlikely that the King will get close enough to capture the Queen, but I guess better safe than sorry.
actually no.
In this position the rook can't be captured because king will be in check. also the queen can't be captured because the rook covers the seventh rank so the king can't go past the rook.
I was watching a stream and the streamer was finishing the game off with a Queen and Rook against a King. He was setting up the ladder and said that the Rook should be the piece closest to the King, not the Queen.
Why though?