«وَكَذَا مَنْ يَنْفَرِدُ عَنْهُ إِذَا كَانَ مُتَأَهِّلًا لِذَلِكَ»
Likewise, the person who alone reports from him may authenticate him if qualified to do so.
Sometimes the sole student is genuinely familiar with his teacher and has the competence of a hadith critic. In such a case, his assessment need not be discarded merely because no other pupil is known to report from that teacher.
But being a student and being competent to evaluate transmitters are distinct attributes. A person may transmit without having the expertise needed for biographical authentication. And even valid narrator authentication does not dispense with investigating connectivity, precision, shudhūdh, or hidden defects in the specific report.