When you disable your Shopify integration after your products have been exported the product list you exported to Shopify will be updated whenever you update its source data. However, those updates won't be sent to Shopify as the integration has been disabled.
Enabling the integration again will not trigger an update on Shopify. If you want to trigger the update on Shopify you will need to re-enable the integration first and then update the source data. This will trigger an export which will send the updated list to Shopify.