"The word nirgranthāḥ is used as an adjective, and api is used in the sense of certainty. For instance, rāmaś ca kṛṣṇaś ca means that both Rāma and Kṛṣṇa enjoy walking in the forest.
Because it is said that both Rāma and Kṛṣṇa enjoy wandering in the forest, it is understood that both of Them are enjoying Their tour within the forest.