Which indexer is used for the Product Stock Update Magento 2?
If you are updating Product stock status value from the Product page with a click on Advanced inventory, new modal form display stock related data for the product.
When you are updating only Product stock related data, You need to reindex only the cataloginventory_stock index to see changes.
CLI Command : php bin/magento indexer:reindex cataloginventory_stock
When you run this command, the cataloginventory_stock_status table data is updated from the cataloginventory_stock_item table.