TYPO3 Core

Adding anything to PAGE like:

10 = USER
10 {
    userFunc = TYPO3\CMS\Extbase\Core\Bootstrap->run
    extensionName = TcSeo
    controller = Sitemap
    pluginName = SeoXml
}

with ordinary ext_localconf.php

ExtensionUtility::configurePlugin(
    'TcSeo',
    'SeoXml',
    [SitemapController::class => 'xml']
);

still works when:
I am logged in as admin
Not logged in in BE
But does NOT work when Im logged in BE as editor....
For some reason this comes up:

The default controller for extension "TcSeo" and plugin "SeoXml" can not be determined. Please check for TYPO3\CMS\Extbase\Utility\ExtensionUtility::configurePlugin() in your ext_localconf.php.

• We've tried with the newly introduced EXTBASEPLUGIN as well, which yields the same result
• Additionally I've found that it stems from the ConfigurationManager instance used, being wrong. When logged in as a non-admin user, when it injects the TYPO3\CMS\Extbase\Configuration\ConfigurationManager no TYPO3_REQUEST is found and therefore the concreteConfigurationManager is set to BackendConfigurationManager which of course does not contain the correct information about the plugins