DNS servers are usually set as an IP address, not a hostname. So for example the DNS server in your NAS is set to 192.168.0.5.
The queries will go to that IP address.
Having them go to pfsense.hooper.com would be putting the cart before the horse: how should it know where to look up “pfsense.hooper.com” if the dns server is not set? You have to tell it the DNS server IP to go to first, then it can resolve hostnames.
Maybe show us the network settings for your NAS.