Can't resize lvm backup volume storage

Sorry, I think I never got rid of this problem :

incus storage volume show default custom/backups-vol
config:
block.filesystem: ext4
block.mount_options: discard
size: 160GiB
description: ""
name: backups-vol
type: custom
used_by: []
location: none
content_type: filesystem
project: default
created_at: 2025-05-29T22:51:00.353476482Z

incus storage volume list default
+-----------------+-------------------------+-------------+--------------+---------+
|      TYPE       |          NAME           | DESCRIPTION | CONTENT-TYPE | USED BY |
+-----------------+-------------------------+-------------+--------------+---------+
| container       | tututut                 |             | filesystem   | 1       |
+-----------------+-------------------------+-------------+--------------+---------+
| container       | toutoutoutou            |             | filesystem   | 1       |
+-----------------+-------------------------+-------------+--------------+---------+
| custom          | backups-vol             |             | filesystem   | 0       |
+-----------------+-------------------------+-------------+--------------+---------+
| custom          | images-vol              |             | filesystem   | 0       |
+-----------------+-------------------------+-------------+--------------+---------+
| virtual-machine | tatatatataa             |             | block        | 1       |
+-----------------+-------------------------+-------------+--------------+---------+
| virtual-machine | tatatatii               |             | block        | 1       |
+-----------------+-------------------------+-------------+--------------+---------+

Then why I have this error ?

incus storage volume set default custom/backups-vol size=50GiB
Error: In use
r00t@w00t:~# incus storage volume delete default custom/backups-vol
Error: The storage volume is still in use

As I got stuck as I tried to explain here in this other post (so sorry for the mess btw), I’m looking for some disk space :
pvs
PV VG Fmt Attr PSize PFree
/dev/mapper/nvme0n1p3_crypt tatati-vg lvm2 a-- 406.17g 0

Thanks a lot to anyone involved in incus <3