WordPress Block Context inheritance

add_filter( 'render_block_context', function( $context, $parsed_block ) {
    if ( 'core/query' === $parsed_block['blockName'] ) {
        $context['helga/tacos'] = 'we love tacos';
    }
    return $context;
}, 10, 2 );

add_filter( 'block_type_metadata', function( $metadata ) {
    if ( 'core/query' === $metadata['name'] ) {
        $metadata['attributes'] ??= [];
        $metadata['attributes']['tacos'] = [
            'type' => 'string',
            'default' => 'default tacos',
        ];

        $metadata['providesContext'] ??= [];
        $metadata['providesContext']['helga/tacos'] = 'tacos';
    }
    if ( 'core/post-title' === $metadata['name'] ) {
        $metadata['usesContext'] ??= [];
        $metadata['usesContext'][] = 'helga/tacos';
    }
    return $metadata;
} );

add_filter( 'render_block_core/post-title', function( $block_content, $block, $instance) {
    $context = $instance->context['helga/tacos'] ?? 'no tacos'; // This is never set.
    return '<p>context $taco: ' . $context . '</p>';
}, 10, 3 );