Seems like this might be the cause of composer install creating a /Plugin root folder and installing every package that has a type: cakephp-plugin in their own composer.json into that (tracked) folder.
It's not clear to me how to detect whether this plugin is being composer installed via composer v1 or v2, but on the master / 4.x branch it's probably safe to remove composer/installers from the composer.json file in THIS project.
The issue is fixed when a different project that runs composer require loadsys/cakephp-config-read:~4.0 should NOT end up with a root Plugin/ folder when running composer install.