We're currently progressively updating CommonSettings.php to load extensions through wfLoadExtension instead of former include, to comply with extension registration and get rid of wmg/wg hack (see T119117).
Humans are quite bad to spot typos when extensions path or name look coherent, but this is potentially very harmful for the servers, as any deployment could break (and actually broke) the servers.
To avoid this, we can add tests to CommonSettings.php (and CommonSettings-labs.php): any wfLoadExtension method call should be validated, to ensure it requires to load an actual extension.
Related incident: https://wikitech.wikimedia.org/wiki/Incident_documentation/20160601-MediaWiki