Why does the arhat of the fourth fruit possess a liberation realization equivalent to that of an eighth-bhūmi bodhisattva?

Arhats of the fourth fruit in the Small Vehicle can enter nirvāṇa without remainder (anupadhiśeṣa-nirvāṇa). In the Mahāyāna, bodhisattvas from the first bhūmi onward are noble ones of the third fruit who have eliminated afflictions. Although bodhisattvas on the bhūmis can enter the correct position of liberation and attain the fourth fruit, if they were to attain it, they would have to enter nirvāṇa without remainder upon death. Therefore the Buddha does not permit bodhisattvas to attain the fourth fruit and enter the correct position of liberation, until they reach the full mind of the seventh bhūmi, at which point they attain the fourth fruit and enter the eighth bhūmi. Bodhisattvas of the eighth bhūmi and above will no longer enter nirvāṇa without remainder. Thus, from the perspective of the realization of liberation, the fourth fruit and the eighth-bhūmi bodhisattva are equal in their liberative realization. Even at the full mind of the first bhūmi, one may not attain the fourth fruit; otherwise it would violate the Buddha's precepts and incur the Buddha's rebuke. The Buddha will also protect bodhisattvas so that they do not attain the fruit of the fourth fruit.