Customers data being reindexed each time when setup:upgrade command is running. Actual for magento 2.3.* (no need for 2.4) Install this module to your vendor
composer require robolv/magento-customer-indexer-fix
And after enable module in magento
bin/magento mo:en Robo_CustomerIndexerFix
Issue reported here: magento/magento2#19469