Codeigniter 4.2 Auto Routing weird thing happening

In CI4.2 it says in the route file:

Code:

// The Auto Routing (Legacy) is very dangerous. It is easy to create vulnerable apps
// where controller filters or CSRF protection are bypassed.
// If you don't want to define all routes, please use the Auto Routing (Improved).
// Set `$autoRoutesImproved` to true in `app/Config/Feature.php` and set the following to true.
//$routes->setAutoRoute(false);

Is my understanding correct that the new feature requires developers to manually add a route for every single new static link/url? and that if the "Improved" auto routing is enabled that it would not require the developer to manually add every single static url?

Because I tried upgrading my website to CI4.2 and lo and behold every ajax request is not working, just 404 page not found... even when I enabled the "Improved" auto routing and the $routes->setAutoRoute(true) set to true... is that a bug?