It does not. It doesn’t quite not say it, either:
1) At 15, Voldemort creates his first Horcrux from Abagail Myrtle.
2) After he “grasp[s] the stupidity of ordinary people”, Voldemort decides to invent a better ritual.
3) He spends “years” refining it in his imagination.
4) Quirrel finds one of the Horcruxes which Voldemort had hidden in the “hopeless idiocy of [his] youth”
So, is “when he grasped the stupidity of ordinary people” + “years” < “youth”? It seems unlikely. But I do not think that it is quite ruled out.
It does not. It doesn’t quite not say it, either:
1) At 15, Voldemort creates his first Horcrux from Abagail Myrtle.
2) After he “grasp[s] the stupidity of ordinary people”, Voldemort decides to invent a better ritual.
3) He spends “years” refining it in his imagination.
4) Quirrel finds one of the Horcruxes which Voldemort had hidden in the “hopeless idiocy of [his] youth”
So, is “when he grasped the stupidity of ordinary people” + “years” < “youth”? It seems unlikely. But I do not think that it is quite ruled out.