collection.php

<?php
/**
 * Collection Products
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/single-product/related.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see         https://docs.woocommerce.com/document/template-structure/
 * @package     WooCommerce\Templates
 * @version     3.9.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

if ( $collection_products ) :

	?>

	<section class="collection products">

		<?php
		$heading = 'Товары из коллекции ' . $collection_name;

		if ( $heading ) :
			?>
			<h2><?php echo esc_html( $heading ); ?></h2>
		<?php endif; ?>

		<?php woocommerce_product_loop_start(); ?>

		<?php foreach ( $collection_products as $collection_product ) : ?>

			<?php
			$post_object = get_post( $collection_product->get_id() );

			setup_postdata( $GLOBALS['post'] =& $post_object ); // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited, Squiz.PHP.DisallowMultipleAssignments.Found

			wc_get_template_part( 'content', 'product' );
			?>

		<?php endforeach; ?>

		<?php woocommerce_product_loop_end(); ?>

	</section>
<?php
endif;

wp_reset_postdata();

woocommerce.php

	/**
	 * Вывод товарв по аттрибуту (здесь: аттрибут Коллекция)
	 *
	 * @testedwith    WooCommerce 5.5
	 * @author        Artem Abramovich
	 */
	public function woocommerce_collection_products(): void {

		global $product;

		if ( ! $product ) {
			return;
		}

		$args = [
			'attribute'      => 'kollekcziya',
			'values'         => '',
			'posts_per_page' => 6,
			'columns'        => 6,
			'orderby'        => 'title',
			'order'          => 'desc',
		];

		$collections = $this->get_attribute_slug( $product, $args['attribute'] );

		if ( ! $collections ) {
			return;
		}

		$ordering_args = WC()->query->get_catalog_ordering_args( $args['orderby'], $args['order'] );

		$args_query = [
			'post_type'           => 'product',
			'post_status'         => 'publish',
			'ignore_sticky_posts' => 1,
			'orderby'             => $ordering_args['orderby'],
			'order'               => $ordering_args['order'],
			'posts_per_page'      => $args['posts_per_page'],
			'fields'              => 'ids',
			'tax_query'           => [
				'relation' => 'OR',
				[
					'taxonomy' => 'pa_' . $args['attribute'],
					'terms'    => $collections,
					'field'    => 'slug',
					'operator' => 'IN',
				],
			],
		];

		$cache_key   = sprintf( 'collection_by_product_%s', $product->get_id() );
		$cache_group = sprintf( '%s_%s', $args['attribute'], implode( '_', (array) $collections ) );

		$found    = false;
		$products = wp_cache_get( $cache_key, $cache_group, $found );

		if ( false === $found ) {

			$products = get_posts( $args_query );

			wp_cache_set( $cache_key, $products, $cache_group, 10 );
		}

		$args['collection_name']     = $product->get_attribute( $args['attribute'] );
		$args['collection_products'] = array_filter( array_map( 'wc_get_product', $products ), 'wc_products_array_filter_visible' );

		// Set global loop values.
		wc_set_loop_prop( 'name', 'collection' );
		wc_set_loop_prop( 'columns', apply_filters( 'woocommerce_related_products_columns', $args['columns'] ) );

		wc_get_template( 'single-product/collection.php', $args );
	}