TYPO3 Core

If just some fields are fetched, it is not possible to use the TCA setting label_alt if its field is not part of the defined fields.

To test:

Add this to Configuration/TCA/Overrides/tt_content.php or change in typo3/sysext/frontend/Configuration/TCA/tt_content.php

$GLOBALS['TCA']['ctrl']['label_alt']  = 'rowDescription';
$GLOBALS['TCA']['ctrl']['label_alt_force'] = true;

fill the description field and check the element browser > the description won't be shown as label.

patch the core, reload element browser