成唯識論述記 3.210

3.210

述曰：下分別之，此釋見分若時現量，應為第三果難也。但由見分似外、緣外故名為外，非體是外，故此現量亦不緣三；後二名內，體是內，緣內故。

The Commentary states: Below, it distinguishes them. This resolves the objection that if the darśanabhāga were sometimes direct perception, it ought to serve as the result of the third part. It is solely because the darśanabhāga resembles the external and cognizes the external that it is called 'external', not that its entity is external; hence this direct perception also does not cognize the third part. The latter two are called 'internal' because their entities are internal and they cognize what is internal.