Is the following quote in conventional lanaguge?

DN 1 states the view of nihilist wanderers, as follows: > *Herein, bhikkhus, a certain recluse or a brahmin asserts the following doctrine and view: ‘The self, good sir, has material form; > it is composed of the four primary elements and originates from father > and mother. Since this self, good sir, is annihilated and destroyed > with the breakup of the body and does not exist after death, at this > point the self is completely annihilated.’ In this way some proclaim > the annihilation, destruction, and extermination of an existent > being.* Is the word 'self' used here in conventional language? Or does the word 'self' here actually represent a belief in self by those nihilist wanderers? If those nihilist wanderers did not believe in 'self' ( and thus used 'conventional language'), why were they not considered to be enlightened?