I remember I saw an old film of Sugar Ray Robinson and he was holding excessively, and the commentators were commending him on holding as much as possible when the fight came close quarters. SRR wasn't holding as much as Ruiz, of course, but it wasn't frowned upon as it is now in the game.

I think the 15th round was for fighters who didn't like holding excessively. The other fighter was tired by then and his grasp/hold wasn't as strong, so you could use your brute force to make openings. Now 15th is gone.