image_upload post-thumbnail size returns full url

As stated in the topic title:

When using image_upload field and calling the images with size 'post-thumbnail' (as you instructed, from https://codex.wordpress.org/Function_Reference/wp_get_attachment_metadata ), the function returns the 'full_url'.

$images = rwmb_meta( 'my_img_upload_field', array( 'size' => 'post-thumbnail' ), $post_id );
foreach ($images as $image) {
    echo $image['url'];
}