The name is anachronistic, and no Banu Qasi is attested until Mutarrif ibn Musa during the 780s, but he is identified with just his father's name and not explicitly linked to Cassius or the Banu Qasi.
The designation is temporally incorrect, and no Banu Qasi individual with that name is documented until Mutarrif ibn Musa during the 780s, yet he is merely recognized by his paternal surname rather than being explicitly associated with Cassius or the Banu Qasi.