Inner Blocks allowedBlocks property doesn't work

Hey there,

i'm in the process of creating a new site with mb_blocks and a custom theme. I've installed MB using composer and everything works fine.

Now, I wanted to add my first block "hero" and it seems that allowedBlocks doesn't work as expected.

I have the following code

functions.php:

/**
 * Block Register
 */
add_filter('rwmb_meta_boxes', function ($meta_boxes) {
    $block_files = glob(get_template_directory() . '/blocks/mb/*/block.php');

    if (! empty($block_files)) {
        foreach ($block_files as $block_file) {
            $meta_boxes[] = require $block_file;
        }
    }

    return $meta_boxes;
});

block.php:

<?php
return [
    'title'           => 'Hero Content',
    'id'              => 'hero-content',
    'description'     => 'A custom hero content block',

    // Block settings.
    'type'            => 'block',
    'icon'            => 'awards',
    'category'        => 'layout',
    'context'         => 'side',
    'render_template' => get_template_directory() . '/blocks/mb/hero/template.php',
    // 'enqueue_style'   => get_template_directory_uri() . '/blocks/mb/hero/style.css', // CSS am besten auch hier ablegen
    // 'supports' => [
    // ],
    'fields'          => [
        [
            'type' => 'file_advanced',
            'id'   => 'media',
            'name' => 'Media',
            "max_file_uploads" => 1,
            'mime_type' => 'video/mp4,image/*',
            'desc' => 'Upload an image or a video (mp4).',
        ]
    ],
];

template.php:

<?php
$media_outer_array = $attributes['media'] ?? null;
// reset() holt den Wert des ERSTEN Elements, egal welchen Key es hat.
$media = $media_outer_array ? reset($media_outer_array) : null;
$is_video = false;

if ($media) {
    if (isset($media['mime_type']) && str_starts_with($media['mime_type'], 'video/')) {
        $is_video = true;
    }
}
?>

<div class="hero-block">
    <?php if ($media):
    ?>
        <?php if ($is_video):
        ?>
            <video controls muted autoplay loop playsinline>
                <source src="<?= esc_url($media['url']); ?>" type="<?= esc_attr($media['mime_type']); ?>">
            </video>
        <?php else:
        ?>

            <img src="<?= esc_url($media['url']); ?>" alt="<?= esc_attr($media['title']); ?>">

        <?php endif; ?>
    <?php endif; ?>
    <div class="hero-content">
        <h1><?php echo esc_html($title); ?></h1>
        <p><?php echo esc_html($content); ?></p>
        <InnerBlocks
            template="<?= esc_attr(json_encode([
                            ['core/heading',   ['placeholder' => 'Titel eingeben...', 'level' => 1]],
                        ])) ?>"
            allowedBlocks="<?= esc_attr(json_encode([
                                'core/heading',
                            ])) ?>" />
    </div>
</div>

For some reason i can still insert any block i want as Innerblock. Anyone an idea what is going wrong here?