Am I missing something in relations yii2?

Question

Yii

Hello. There is a question regarding relations in yii2. I have three tables: products, files, files_thumb. Files is related to products and thumbs is related to files. I need to select certain products with full photos and thumbnails, while full photos are selected by a certain parameter, not all.
In the products model, I write the following relations:

public function getFile() {
        return $this->hasMany(Files::className(), ['id_obj' => 'id']);
    }

    public function getThumbs(){
        return $this->hasMany(FilesThumb::className(), ['id_file' => 'id'])->via('file');
    }

The selection condition is such that files.onmain = 1;
I make a request:

$res = ShopProducts::find()->joinWith('thumbs')->where("files.onmain=1")->all();

The query itself is built correctly, but explain to me why, when I print $res, I see all the files, including those that do not fall under files.onmain=1, and when I print $res->thumbs, I see only that need.
Please explain what is happening here, what does he really choose? Thanks in advance for your replies.