«حَدَّثَنِي الْحَارِثُ» explicitly represents al-Ḥārith narrating directly to al-Shaʿbī; “I heard al-Shaʿbī” explicitly describes Mughīrah’s hearing. By contrast, «عَنْ إِبْرَاهِيمَ أَنَّ الْحَارِثَ قَالَ» does not itself state that Ibrāhīm directly heard al-Ḥārith.
Lack of an explicit hearing formula does not by itself prove a broken chain either. Chronology, evidence of meeting or hearing, alternative routes and the transmitter’s usage must be examined.