The way I remember reading it was that MacArthur himself used four pens to sign the surrender documents. He signed for the United Nations, Adm. Nimitz for the US. One was given to Wainwright, one to Percival, one sent to West Point, and the last given to Jean, his wife.
You could very well be right. My only knowledge is from having seen that portion of the film footage, where he called those two generals to the table.