What is the meaning of Ibn al-Mundhir's statement concerning scholarly consensus (ijma'): "She is with him upon three pronouncements of divorce (talaqat)" in the case of the wife's return?

Whoever divorces his wife three times, she becomes irrevocably separated from him (baynunah kubra), and she is not lawful for him until she marries another husband with a valid marriage, intended to be continuous, and then he divorces her after consummating the marriage. Only then is it permissible for her first husband to marry her with a new contract and a new dower, and she returns to him with three new divorces.