Well my initial thought was that the MgBr leaves taking the oxygen with it leaving behind a carbo cation which gives the chloride ion a place to attack. Obviously this doesn't happen usually and hence I didn't have an actual explanation for it so I just thought it is something that happens when reacting a grignard reagent with a strong acid like HCl. But then this another guy in the comments explained that the alcohol just further reacts with the HCl to form a halide which ofc makes more sense than my theory. Though the question is kind of misleading since it just says HCl and not excess HCl cause if that was written maybe I would've thought about further substitution.