TYPO3 Core

I have an extension that works with the Superclass/Subclasses Singletable-Domainmodel-Inheritance pattern.

If i place the extbase peristence configuration in a Typoscript file and include it like this in ext_localconf.php
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addTypoScriptSetup(
'<INCLUDE_TYPOSCRIPT: source="FILE:EXT:EXTKEY/Configuration/TypoScript/FrameworkConfiguration.ts">'
);

Everything works.

Now i wanted to change this to a more api-way and moved that file to /ext_typoscript_setup.txt

If i do so a fatal error is thrown:
Fatal error: Cannot instantiate abstract class Vendor\Package\Domain\Model\ModelName in /var/www/project/typo3_src/typo3/sysext/extbase/Classes/Object/Container/Container.php on line 121

So there seems to be something wrong in the bootstrap. For some Reasong an instance of the model is created without reason. But if done via the addTypoScriptSetup way its not - so that is odd.

Version used is 7.2

I will upgrade to 7.3 today and tell you if the issue is still present.