Hi when running composer test it errors out and says this setting lacks wg prefix. But this setting should have wg since it is for the path to the extension for example timedmediahandler $timedMediaDir which has the DIR set. It should only show that error if it isent setting DIR.
I am not sure if this is done on purpose or if it should change but same goes for mediawiki core when setting $IP which has been like that for a long time and would break anything if it is changed.