Lxc copy –refresh always copies the full virtual machine?

I have Cluster A and Cluster B built with microcloud.
The version of LXD is 5.19 on both clusters.
The storage type is Ceph on both cluster, same version 17.2.6.

In Cluster A, I have configured B as a remote.

I would like to copy a virtual machine from A to B. The virtual machine has a snapshot named snap-0. The first time, it performs a full copy as expected. However, subsequently, I expect the copy to be incremental, but this is not happening.

The commands I execute are:

lxc copy v1 B:v1 → full copy
lxc copy v1 B:v1 --refresh → it should perform an incremental copy, but a full copy is happening

Is it possibile to perform incremental copy with virtual machine?