If divorce is pronounced by an ambiguous term, why must it be revocable unless three pronouncements occur?

Primary text

Divorce issued by an ambiguous term concerning a consummated wife, absent any financial consideration or completion of the permissible count of divorces, must be revocable (*raj'i*), following the precedent set by explicit divorce and other types of ambiguous pronouncements where revocability is agreed upon. If it is argued that these terms imply finality, then three such pronouncements should logically result in definitive separation (*baynuna*), as a consummated wife cannot be definitively separated except through three pronouncements or compensation.