Because with the buildin php server we use php cli directly as server, we do not have Apache, so we are using a very simple php code to emulate htaccess routing. That code might need improvments indeed.
You can check the code if you want it is in the indicated path file called htaccess_router.php
Just to echo I have the same issue as @Hyperbytes in 6.0.5 - I am running on a Mac - php v 8.2.
The solution works for me also.
The file to edit is not actually in your project folder. On a Mac you can right click on the Wappler Application icon and “Show package contents” - then browse to the path.