俱舍論疏 24.41

24.41

論「二上流者至極七返生」，釋二上流未至色究竟天及有頂天，皆容中間般涅槃也。如生二、三、四天等處中間般涅槃者是半超攝，雖不隔越，以超生故亦名半超。

On the treatise passage, "The two upstream practitioners... taking birth at most seven times": This explains that before reaching Akaniṣṭha Heaven and Bhavāgra Heaven, both upstream practitioners may attain parinirvāṇa in the intermediate stages. Just as those who attain parinirvāṇa in intermediate places upon being reborn in the second, third, or fourth heavens are subsumed under intermediate traversers, even if they do not skip over stages, they are still called intermediate traversers because they traverse births.