Looking at Lily's stats, her specialty could be seen at a glance. Having already seen Stella's stats, he wasn't surprised by her status.
He was even a little disappointed that she didn't have a King Rank skill, as it could influence her upper limit greatly.
Let just take her skill 'Elemental Burst'; there is no limit for energy collection on it. Theoretically, if she collects enough energy, her attack will have more destructive power than that of a False God.
But if she attacks a False God, even a Mortal King with that attack, it won't be able to injure them. That is the distinction between below Mortal King rank and above.
As the saying goes, general against general and soldier against soldier, a king can only be hurt by another king.
So, even a small swing of Stella using her King rank skill has the possibility of injuring a King, but a full attack of Lily won't be able to do that.