How are you determining that the server is forwarding the request? The server receiving the request and the server forwarding the request are two different things. Have you run a packet capture on the server to verify that the server is forwarding the request?
The behavior, except for the forwarding if that is actually happening, is perfectly normal when using nslookup and submitting a query that isn't fully qualified. You omitted the trailing dot (.) in your query (google.com instead of google.com.) and as such the local DNS suffix (primary and/or connection specific) will be appended to the query when submitting it to the server. This is a function of nslookup and not the DNS client itself. See here for clarification:
I ran a test using my DNS servers and my DNS servers did not forward the request with the local DNS suffix. They only forwarded the request after the local DNS suffix had been stripped.
I've included 2 screen shots to illustrate my point. In the first screenshot you can see my nslookup query from the client with debugging turned on. In the second you can see the DNS traffic as captured on my server. You'll see clearly that the server receives the requests with and without the local DNS suffix appended but only forwards the query once the local DNS suffix has been stripped off.