Thanks for taking the time to report this! Confirming.
I wonder if that happens because once it refers to audio, and once to video.
$:andre\> grep -r "Permitted file types" .
'upload-permitted' => 'Permitted file types: $1.',
$:andre\> grep -r "upload-permitted" .
$this->msg( 'upload-permitted', $this->getContext()->getLanguage()->commaList( $wgFileExtensions ) )->parseAsBlock() .