The fact that magical talent could increase until the 20 years of age was public knowledge, which allowed Lith to showcase the progress of his core whereas Vastor had to hid his own.
The magical community valued people like Manohar, Kwart, and Ainz not only because of their genius, but also because of the violet light in their eyes. For the same reason, once Vastor had reached 20 and remained bright blue, he had been classified as a second-rate genius.
'This stupid game allowed me to kill two birds with one stone.' The King thought. 'I foiled Deirus's plan and I finally confirmed my suspicions. Lith is an Awakened. Amazing talent my royal ass, the only way he could beat Kwart was with body casting.
'Still, reaching the violet core at nineteen is even more impressive, unless Lady Faluel the Hydra taught him, of course. Yet this will be a question for another day.'