Does an Arhat's Entry into Nirvāṇa Equal Entry into the Tathāgatagarbha?

The seven consciousnesses and five aggregates of an arhat are entirely generated and sustained by the tathāgatagarbha; there has never been a single moment when they could exist independently apart from the tathāgatagarbha. Therefore, an arhat has never been outside the tathāgatagarbha, and still less can he enter into it; otherwise, the arhat would be an unborn and unceasing dharma-body that exists originally without cause or condition, equivalent to the tathāgatagarbha. Thus, when an arhat enters nirvāṇa, it is not a matter of entering the tathāgatagarbha. Nirvāṇa is a state in which the tathāgatagarbha exists alone, without the seven consciousnesses and five aggregates. Although in this state there is only the tathāgatagarbha and no other dharmas, it is still a state in which the tathāgatagarbha abides alone, not conjoined with the seven consciousnesses and five aggregates. If nirvāṇa refers to such qualities as being unborn and unceasing, neither increasing nor decreasing, pure and undefiled, then the tathāgatagarbha possesses the nature of nirvāṇa. But the tathāgatagarbha is not identical to nirvāṇa, because the tathāgatagarbha has many other qualities and other states as well; nirvāṇa is not entirely equivalent to the tathāgatagarbha. The tathāgatagarbha is the substance, while nirvāṇa is the quality and state of that substance.