tran_destroy_pkt is presumably not an alternative to itself in tran_setup_pkt(9E)
tran_setup_pkt(9E), we have the following sentence:
The tran_setup_pkt() and tran_destroy_pkt() vectors in the scsi_hba_tran(9S) structure are alternatives to the tran_init_pkt() and tran_destroy_pkt() entry points.
tran_destroy_pkt() is not an alternative to itself. This was almost certainly meant to be 'The tran_setup_pkt() and tran_teardown_pkt() vectors in the scsi_hba_tran(9S) ...'.