create zpool from zvols?

Hello, I am using ZFS on FreeBSD 13.0-RELEASE-p8. For experimentation 
and demonstration, I would like to create zpools using zvols as the 
underlying block devices.

For example, I have these:

[root@ibex] # zfs list -r -t volume zroot | grep zv
zroot/zv0              8.25G   832G       56K  -
zroot/zv1              8.25G   832G       56K  -

This seems as if it would do what I want:

[root@ibex] # zpool create -n ztest mirror /dev/zvol/zroot/zv{0,1}
would create 'ztest' with the following layout:

	ztest
	  mirror
	    zvol/zroot/zv0
	    zvol/zroot/zv1

But when I try to actually do it, it doesn't work:

[root@ibex] # zpool create ztest mirror /dev/zvol/zroot/zv{0,1}
cannot create 'ztest': no such pool or dataset

FWIW, doing something similar on OmniOS works fine:

[root@orca] # uname -srvp
SunOS 5.11 omnios-r151040-852962cae3 i386
[root@orca] # zfs create -V 2G rpool/zv0
[root@orca] # zfs create -V 2G rpool/zv1
[root@orca] # zpool create ztest mirror /dev/zvol/dsk/rpool/zv{0,1}
[root@orca] # zpool status ztest
   pool: ztest
  state: ONLINE
   scan: none requested
config:

         NAME                         STATE     READ WRITE CKSUM
         ztest                        ONLINE       0     0     0
           mirror-0                   ONLINE       0     0     0
             /dev/zvol/dsk/rpool/zv0  ONLINE       0     0     0
             /dev/zvol/dsk/rpool/zv1  ONLINE       0     0     0

errors: No known data errors

I thought I had done this in the past. Am I doing something wrong? Am I 
misremembering and this never worked?

Using files created with truncate(1) rather zvols seems to work fine so 
maybe that's what I did before. Not sure, it's been a long time since I 
wanted to do something like this.

Thanks for any enlightenment.