Izroth was always on a constant mission to improve himself in order to reach the pinnacle of this world. In order to do that, it required that he learned from small and big experiences alike.
However, while Izroth was busy reflecting on his battle and looking for ways to improve if he had to confront his opponent again, Ourami had never set Izroth in his sights. And, even if the pillar did miraculously view Izroth as his equal, he still would not have lingered on that one battle in an attempt to improve himself.
From what Izroth knew about the pillars, Ourami was someone born with both strength and talent. Of course, this was not a bad thing and could be considered a huge blessing. But, there was never a drive present past wanting to maintain his authority. After all, with his strength and talent, eventually, he would reach an even higher stage.