Qadhf is an accusation of illicit sexual intercourse, for which the exact language matters greatly. The source considers a speaker who refers to such an accusation and another person who responds “ṣadaqta” (“You spoke truly”).
That response may affirm that the first speaker uttered those words, without necessarily affirming the truth of the underlying accusation. Because the acknowledgement is open to different senses, an explicit accusation cannot simply be inferred for the purpose of imposing the prescribed penalty.
The example shows why semantic ambiguity has especially important consequences where penal liability is concerned.