Marijn "i before j" van Putten 30 Apr 18
Replying to @PhDniX
ʾAbū Ǧaʿfar indeed is a Hijazi reader (Medina). And this document indeed also vocalises -hū after genitive nouns (see AaHLiHu = ʾahlihū). It therefore seems that this (and other?) Hijazi readings have been classicized somewhat over time, generalizing the -i-hī forms.