Not sure if this was intended, but it's annoying me. In my callback, where $request is WP_REST_Request object and I do this:

$params = $request->get_params();
$zero = $request->get_param( 0 );

I get a 0 index in $params and $zero has the route URL. I don't see why it should be a param, it's not registered on the endpoint, and its redundant to what I can get with the get_url_params() method.