In fact I'm not saying that internal web content
must be cached. It's all matter of network topology, content and proxy definition. This is in fact another debate.
Having "no proxy" for internal server is very often used.
But in case one wants to use Zentyal as non-transparent proxy for internal server, then Zentyal MUST be able to resolve internal servers using.... quite often Zentyal DNS, meaning very often itself
Look for instance at two sites linked with VPN. What if you want to access web server running on remote site benefiting from proxy in the middle to reduce bandwidth? I obviously assumes you are not running transparent proxy here because in such case, name is resolved by client
I also hope that Zentyal will, in next versions, be able to distribute mail to internal mail servers, to "really" replicate will ldap server using server name, not IP address. And this can be extend to any "non Zentyal" application one may have installed on Zentyal server itself, requiring to communicate with any other internal machine using FQDN instead of IP...
So I should stop trying to explain why it should use itself as DNS but instead reverse the question: why should Zentyal not use itself as primary DNS?
Is it weird?