Does $setOnInsert not work with a projection?

mongowtf.php

<?php
$mongo = new \MongoClient();

$col = $mongo->testDb->testCollection;

$col->drop();

// only returns the `_id` attribute, despite the "fields" argument
var_dump($col->findAndModify([
    'test' => 'one',
], [
    '$setOnInsert' => ['test' => 'one'],
], ['test'], [
    'upsert'    => true,
    'new'       => true,
]));

$col->drop();

// includes the `test` attribute as well as `_id`
var_dump($col->findAndModify([
    'test' => 'two',
], [
    '$setOnInsert' => ['test' => 'two'],
], null, [
    'upsert'    => true,
    'new'       => true,
]));

shell.bash

local> mongo test123
MongoDB shell version: 3.0.2
connecting to: test123
Server has startup warnings: 
2015-08-21T16:35:12.578-0400 I CONTROL  [initandlisten] 
2015-08-21T16:35:12.578-0400 I CONTROL  [initandlisten] ** WARNING: soft rlimits too low. Number of files is 256, should be at least 1000
> db.test.find()
> db.testCollection.findAndModify({query: {test: 'one'}, update: {$setOnInsert: {test: 'one'}}, fields: ['test'], upsert: true, new: true });
{ "_id" : ObjectId("55db7e0566a857b7d4f13d1f") }
> db.testCollection.findAndModify({query: {test: 'three'}, update: {$setOnInsert: {test: 'three'}}, upsert: true, new: true });
{ "_id" : ObjectId("55db7e1f66a857b7d4f13d20"), "test" : "three" }