Hints for forwarding a subdomain on a authoritative server

[Tom]

Hi list

Our BIND (9.16.4) is authoritative for zone "example.com". Now I need to 
forward a subzone "sub.example.com" to another nameserver instance on 
the same server, running for example under port 5353:

A few years ago, this topic was already discussed:
https://lists.isc.org/pipermail/bind-users/2009-April/076156.html

My BIND config looks like this:
================== SCHNIPP ==================
zone "example.com" {
         type master;
         file "master/example.com.hosts";
         };
zone "sub.example.com" {
         type forward;
         forwarders { 127.0.0.1 port 5353; };
         forward only;
         };
================== SCHNAPP ==================

In the zonefile for "example.com" I have a delegation like this (as 
described in the post above):

sub.example.com.            IN      NS      subns.example.com.

So, the authoritative server understands not to be responsible for this 
zone and forwards the request to the other nameserver.

But: The zone-forwarding is only working, when I enable "recursion" on 
the authoritative server. Does this means, that zone-forwarding really 
requires recursion? Is there a better way with not enabling recursion 
(perhaps with views) to accomplish this?

Many thanks for any hints.

Kind regards,
Tom