MongoDB PHP aggregate - incorrect data set in output array - mongodb

Question

I'm trying to select data from few documents and output in nested arrays.
Aggregate:
$aggBuilder = $this->documentManager->getDocumentCollection(User::class);
$outputData = $aggBuilder->aggregate([
['$match' => [
'_id' => ['$in' => $usersId]
]
],
['$unwind' => '$articles'],
['$lookup' => [
'from' => 'articles',
'localField' => 'articles._id',
'foreignField' => '_id',
'as' => 'article',
]],
['$unwind' => '$article'],
['$lookup' => [
'from' => 'comments',
'localField' => 'comments._id',
'foreignField' => 'article_id',
'as' => 'article.comment'
]],
['$group' => [
'_id' => [
'id' => '$_id',
'name' => '$name',
'desc' => '$desc',
],
'articles' => ['$addToSet' => [
'id' => '$article._id',
'title' => '$article.title',
'content' => '$article.content',
'comments' => ['id' => $article.comment.id', 'content' => '$article.comment.content'],
]],
]]
],
[
'cursor' => [
'batchSize' => 101,
],
]);
dd($outputData->toArray());
The problem is in part where I try to in every article get collection of comments for this article.
Some reason output looks this:
'Andy Jones' = [
'Article First' = [
'id' = 'sdgdf76g8df',
'title' = 'First Article'
'content' = 'Contetn of article'
'comments' = [
'id' = [
'dfdh54gdfter',
'32gdfhfgh43et',
'34te3gdfgerdt'
],
'content' = [
'content for first article',
'content for second article',
'content for third article'
]
]
]
]
As you see comments are splited in two arrays. One for 'id' and one for 'content'.
What I want is separate array for every comment and in that array data from single comment. Like bellow:
'comments' = [
[0] = [
'id' = 'dfdh54gdfter',
'content' = 'Lorem ipsum 1',
],
[1] = [
'id' = 'dfdg4554er',
'content' = 'Lorem ipsum 2',
],
[2] = [
'id' = 'dfdh54gdfter',
'content' = 'Lorem ipsum 3',
],
]
Thank you.