The two of them still held back during the fight. It was not because they underestimated each other, but rather because they both knew how terrifying their power would be at full capacity. Xiao Lin would definitely not use Myth during a spar, nor was he planning on using his dragon's breath.
However, in that scenario, Xiao Lin was actually on the losing end of things. After all, his abilities were mostly on the explosive side, but Alexander was just using his own strength to fight.
Even though it seemed like Xiao Lin had more than enough power to spare, he was very clear that he had almost run out of time using Ruin. His nerves were on the edge. Even so, his opponent's fists applied tremendous pressure on Xiao Lin.