\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addStaticFile() must go into file Configuration/TCA/Overrides/sys_template.php to benefit from TCA caching. That's not working via ext_tables, according to documentation:
Call this method to add an entry in the static template list found in sys_templates FOR USE IN ext_tables.php FILES or in Configuration/TCA/Overrides/sys_template.php Use the latter to benefit from TCA caching!
According to API documentation,
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addStaticFile()must go into fileConfiguration/TCA/Overrides/sys_template.phpto benefit from TCA caching. That's not working viaext_tables, according to documentation:Follow-Up to #423