Specific to your question, I believe 18.104.22.168 is OpenDNS as well. You can try 22.214.171.124 which is Google’s public DNS to see how it works.
Beyond answering the actual question of why would that be, a better practice for this is to have your clients pointing to your internal DNS server which will use a forwarder to 126.96.36.199 or 188.8.131.52 whichever you choose. It prevents you having to manually set all of them plus you probably don’t want them to bypass the OpenDNS block.
For specific workstations that do need to work around the blocks, use 184.108.40.206 and yours as the secondary. You may need to run flushdns to have it work properly.