as nvmecontrol has sub command ns, and man nvmecontrol didn't descript that part.

root@nec:~ # nvmecontrol 
usage:
       nvmecontrol devlist
       nvmecontrol identify [-x [-v]] <controller id|namespace id>
       nvmecontrol perftest <-n num_threads> <-o read|write>
                            <-s size_in_bytes> <-t time_in_seconds>
                            <-i intr|wait> [-f refthread] [-p]
                            <namespace id>
       nvmecontrol reset <controller id>
       nvmecontrol logpage <-p page_id> [-b] [-v vendor] [-x] <controller id|namespace id>
       nvmecontrol firmware [-s slot] [-f path_to_firmware] [-a] <controller id>
       nvmecontrol format [-f fmt] [-m mset] [-p pi] [-l pil] [-E] [-C] <controller id|namespace id>
       nvmecontrol power [-l] [-p new-state [-w workload-hint]] <controller id>
       nvmecontrol wdc (cap-diag|drive-log|get-crash-dump|purge|purge-montior)
       nvmecontrol ns (create|delete|attach|detach)

root@nec:~ # man nvmecontrol
NVMECONTROL(8)          FreeBSD System Manager's Manual         NVMECONTROL(8)

NAME
     nvmecontrol - NVM Express control utility

SYNOPSIS
     nvmecontrol devlist
     nvmecontrol identify [-v] [-x] <device id> <namespace id>
     nvmecontrol perftest <-n num_threads> <-o read|write> [-p]
                 <-s size_in_bytes> <-t time_in_sec> <namespace id>
     nvmecontrol reset <controller id>
     nvmecontrol logpage <-p page_id> [-x] [-v vendor-string] [-b] <device id>
                 <namespace id>
     nvmecontrol firmware [-s slot] [-f path_to_firmware] [-a] <device id>
     nvmecontrol format [-f fmt] [-m mset] [-o pi] [-l pil] [-E] [-C]
                 <device id> <namespace id>
     nvmecontrol power [-l] [-p -power_state] [-w -workload_hint]
     nvmecontrol wdc cap-diag [-o -path_template] <device id>
     nvmecontrol wdc drive-log [-o -path_template] <device id>
     nvmecontrol wdc get-crash-dump [-o -path_template] <device id>