Fully qualified is about ambiguity, or the lack thereof, and has nothing to do with the number of dots in the name. example.com can only ever resolve one way. Top-level server delegates name service to the example.com zone name servers, and they respond with A records for that host, if any. example on the other hand, is ambiguous. What zone is it in? Depends on local resolver configuration. People on the internet can’t find you with just example.