Laravel Collection - Problema com filter() e chaves de arrays

Collection.php

<?php
$collection = collect(['um', 'dois', 'tres', 'quatro', 'cinco']);

Filtering.php

<?php
$items = $collection->filter(function($item) {
  return $item != 'um' && $item != 'quatro';
})->toArray();

Filtering2.php

<?php
$items = $collection->filter(function($item) {
  return $item != 'um' && $item != 'quatro';
})
->values
->all()
->toArray();

Resulting

[1 => 'dois', 2 => 'tres' , 3 => 'cinco']