In vendor/magento/module-google-tag-manager/view/frontend/layout/catalog_category_view.xml the block_name is defined as category.products.list. But in vendor/magento/module-google-tag-manager/view/frontend/templates/js.phtml there's a for each that uses product_list. The value category.products.list should also be used in js.phtml. This is the correct name of the block.