Permission plugin documentation incomplete and/or plugin behaving wrong

### Problem

I just had tried to import stuff from a network share which does not support/allow to set permissions. On import of some folders I get an error saying "Could not set permissions on .." - That's obviously correct. But the expectation is, that it sets the permission on the destination.

Led to this problem:

On import of some folders I get an error saying "Could not set permissions on .."
Here's a link to the music files that trigger the bug (if relevant):

### Setup

* OS: Debian GNU/Linux 12 (bookworm)
* Python version: Python 3.11.2
* beets version: beets version 2.7.1

My configuration (output of `beet config`) is: (only partial)

```yaml

# --------------- Plugins ---------------

plugins:
- bucket
- convert
- fetchart
- hook
- importadded
- inline
- lastgenre
- musicbrainz
- missing
- permissions
- replaygain
- scrub
- zero
- jdb

import:
write: no
copy: no
move: no

permissions:
file: 664
dir: 775

```

Is this expected behavior? Aka is the documentation just missing this information? Or is it a bug?