Mike continues to embarrass himself.
Here are two counterexamples that use Āl with royal titles, one from pre-Islamic poetry and one from the Hadith tradition:
Pre-Islamic poet al-Aswad ibn Yafur says: “What can I hope for after Āl Muharriq….?” (al-Mufaddaliyyat, no. 44). Lisan al-Arab explicitly identifies Muharriq here as a royal epithet, and in the verse it refers to Imru al-Qays ibn Amr.
As for the Hadith: “A group of Muslims will conquer the treasure of Āl Kisra….” (Sahih Muslim 2919). Here, Kisra functions as a royal title for the Persian ruler, not a personal name.
Rachida also quotes al-Tabari saying that Āl is “most appropriately” used with well-known names, but conveniently omits that Al-Tabari immediately goes on to say: “As for Firawn (referring to Āl Firawn in the verse), it is said to be a name by which the kings of the Amalekites in Egypt were called, just as the kings of Rome were called Caesar or Heraclius, the kings of Persia Kisra, and the kings of Yemen Tubba.” (Tafsir al-Tabari, Qur’an 2:49).
So if Al-Tabari meant that Āl Firawn could only refer to a personal name, why does he himself explain it in that very passage as a designation used for successive Egyptian kings?