Comment # 6 on bug 1017268 from Stanislav Brabec

Yes, fstrim.timer is enabled for all file systems intentionally.

After the latest update, de-duplication works correctly and it provides
trimming once a week for all file systems and devices that support it.

fstrim currently does not have an exclude feature for --all

This is apparently fixed in Leap 15 (my default is BTRFS_TRIM_PERIOD="none").

But it will need some script to perform the fix on upgrade, as standard fillup
keeps previous values.

Something like that:

%post
# BTRFS_TRIM_PERIOD defaults to weekly up to 42.3. If caused duplicated TRIM.
# If fstrim.timer is enabled, set it to none.
if test -l /etc/systemd/system/multi-user.target.wants/fstrim.timer ; then
    sed -i 's/^BTRFS_TRIM_PERIOD="weekly"/BTRFS_TRIM_PERIOD="none"/'
/etc/sysconfig/btrfsmaintenance 2>/dev/null || :
fi