From https://prv-tests.wmcloud.org/diff/viwiki/Skibidi_Toilet
Parsoid is missing
// Use width which is smaller: real image width or user preference width
// Unless image is scalable vector.
if ( !isset( $handlerParams['height'] ) && ( $handlerParams['width'] <= 0 ||
$prefWidth < $handlerParams['width'] || $file->isVectorized() ) ) {
$handlerParams['width'] = $prefWidth;
}https://github.com/wikimedia/mediawiki/blob/master/includes/linker/Linker.php#L393-L398