I think boxrec is wrong. Monzon avenged the Aguilar, Cambriero and Massi defeats. There may have been a few draws that he didn't avenge, but the the three that beat him were all beaten in rematches. Check out another source besides boxrec.
Well, Akinwande had to vacate his WBO belt on fighting Lewis, so you could say he was the 'lineal' WBO champ, I'd say we can count him
Does Jim Jeffries count, or does the fact of his 1910 ill advised comback against Johnson rule him out?