If advancing a level required missing one talent spell each time, it meant that after advancing to a high-level wizard, Levi would have three fewer innate spells than a perfect "Nine Talent Wizard." This would certainly be a severe disadvantage in a wizard's duel.
A single innate spell could take the place of a myriad of ordinary spells.
Moreover, the power of innate spells could continuously increase with the advancement of a wizard's realm.
Even the innate spells mastered during the third-circle period would still be useful when Levi reached the ninth-circle wizard realm.
Without the proficiency panel, Levi might have, like other wizards, hurried to advance to the fourth-circle with just two innate spells.
Since he had this advantage, he wanted to handle it perfectly without regrets, a reflection of Levi's thoughts and attitude.
Of course, choosing innate spells, like creating a third-circle defensive field, was not something to rush.