I tried main branch and tag 2.2.2. It turns out that, as code below, autorehash doesn't trigger migration of keys among nodes.

$options = array(0;
$options['previous'] = $previous_server_list;
$options['autorehash'] = TRUE;
$ra = new RedisArray($server_list, $options);

Is there something missing in https://github.com/nicolasff/phpredis/blob/master/arrays.markdown#readme ?