I believe that may be a bug. You would have to clarify with an admin on Github, but after looking at the parseRequest function in the URLManager class, the code should fallback to traditional route parsing if a pretty url route does not match, which it doesn’t.
As a quick fix you could overide the current URLManager and replace the parseRequest function with this:
public function parseRequest($request)
{
if ($this->enablePrettyUrl) {
/* @var $rule UrlRule */
foreach ($this->rules as $rule) {
if (($result = $rule->parseRequest($this, $request)) !== false) {
return $result;
}
}
if ($this->enableStrictParsing) {
return false;
}
}
Yii::trace('Pretty URL not enabled. Using default URL parsing logic.', __METHOD__);
$route = $request->getQueryParam($this->routeParam, '');
if (is_array($route)) {
$route = '';
}
return [(string)$route, []];
}