Partial backup of remote directory

I want to make use of the backup service of Home Assistant to include remote directories.
I’ve added a new network storage using NFS and defined it as a Share.
When I connect with SSH to my Home Assistant instance, I can see the contents of my share under the folder /share/my_remote_share.

I created a service to run the backup, but the backup is not created:

service: hassio.backup_partial
  homeassistant_exclude_database: true
  folders: /share/my_remote_share
  name: Backup of Remote Share
  location: my_backup_mount

Under the Supervisor logs, I get this:

2024-06-03 11:59:13.236 INFO (MainThread) [supervisor.backups.manager] Found 3 backup files
2024-06-03 11:59:13.257 INFO (MainThread) [supervisor.backups.manager] Found 3 backup files

Am I doing something wrong, or is this not supported by Home Assistant?