成唯識論述記 5.175

5.175

述曰：乘語勢故，論說「我所」言，非實離我別起我所執。由前理故，須文便故，言穩易故，此是語勢。又有義解。

The Commentary states: By virtue of the force of the phrasing, the treatise speaks the words 'my own', not that apart from the self there actually arises a separate grasp of 'mine'. Due to the aforementioned reasoning, and for the convenience of the text, and because the phrasing is smooth and straightforward—this is merely the force of the phrasing. There is also another doctrinal explanation.