file engine path and prefix settings

I see that the prefix setting is getting applied in Cache.php - including default prefix for all specific settings which is good.

However i've tried to understand if prefix gets applied correctly for the current install.

i see

    $this->lookup = $this->prefix . $this->name . '_lookup';
    $this->lock = $this->lock_dir . '/' . $this->prefix . $this->name . '_lock';

leading to something like this when outputting.

prefix-cache_lookup
/tmp/prefix-cache_lock
prefix-cache_views_lookup
/tmp/prefix-cache_views_lock
prefix-cache_filter_lookup
/tmp/prefix-cache_filter_lock
prefix-cache_content_lookup
/tmp/prefix-cache_content_lock
swdx-cache_menu_lookup
/tmp/prefix-cache_menu_lock

Now see - the lock is in /tmp/ - but we've used a configuration with 'path' => '/my/custompath'
The path gets only applied in fileCacheRouterEngine and not for the lock.

I'd have expected to be able to set the same path for two instances but have a separation because of setting a prefix.
(so i'd expect to have prefix as e.g. a basepath/subfolder in the path tree)
Also i'd have expected to see the path settings apply in _lock vars.

Since i can't find those things documented in any location (i was looking for) i hope someone can answer me.