The answer is in the article, and in the definition of Level 3: the automated feature is restricted to a certain operational design domain. For Drive Pilot, this domain comprises specific sections of highway, maximum speed, and certain weather conditions. It refuses to operate outside that domain, even if technically the software might be capable of doing so.
When it detects that it is leaving or has left that domain, it tries to hand back control to the human within a short period, failing which it brings the vehicle to a safe halt and calls for help.