Why does "Mems_allowed_list" from /proc/pid/status file show all numa nodes despite using --membind with numactl only on single node?

Issue

• Why does "Mems_allowed_list" from /proc/pid/status file show all numa nodes despite using --membind with numactl only on single node?

$ numactl --membind 1 sleep 120 &
[1] 1735084

$ mypid=$!

$ grep Mems_allowed_list /proc/$mypid/status
Mems_allowed_list:      0-3

$ cat /proc/$mypid/numa_maps
558c2d256000 bind:1 file=/usr/bin/sleep mapped=7 N0=7 kernelpagesize_kB=4
558c2d45d000 bind:1 file=/usr/bin/sleep anon=1 dirty=1 active=0 N1=1 kernelpagesize_kB=4
558c2d45e000 bind:1 file=/usr/bin/sleep anon=1 dirty=1 active=0 N1=1 kernelpagesize_kB=4
558c2e992000 bind:1 heap anon=1 dirty=1 active=0 N1=1 kernelpagesize_kB=4
7f48da35e000 bind:1 file=/usr/lib64/libc-2.28.so mapped=274 mapmax=91 N0=274 kernelpagesize_kB=4
7f48da51a000 bind:1 file=/usr/lib64/libc-2.28.so
7f48da719000 bind:1 file=/usr/lib64/libc-2.28.so anon=4 dirty=4 active=0 N1=4 kernelpagesize_kB=4
7f48da71d000 bind:1 file=/usr/lib64/libc-2.28.so anon=2 dirty=2 active=0 N1=2 kernelpagesize_kB=4
7f48da71f000 bind:1 anon=3 dirty=3 active=0 N1=3 kernelpagesize_kB=4
7f48da723000 bind:1 file=/usr/lib64/ld-2.28.so mapped=45 mapmax=89 N0=45 kernelpagesize_kB=4
7f48da941000 bind:1 anon=2 dirty=2 active=0 N1=2 kernelpagesize_kB=4
7f48da94e000 bind:1 anon=2 dirty=2 active=0 N1=2 kernelpagesize_kB=4
7f48da950000 bind:1 file=/usr/lib64/ld-2.28.so anon=1 dirty=1 active=0 N1=1 kernelpagesize_kB=4
7f48da951000 bind:1 file=/usr/lib64/ld-2.28.so anon=2 dirty=2 active=0 N1=2 kernelpagesize_kB=4
7ffe55d6b000 bind:1 stack anon=12 dirty=12 active=2 N1=12 kernelpagesize_kB=4
7ffe55db8000 bind:1
7ffe55dbc000 bind:1