The information is listed incorrectly on the packaging of LEGO City Undercover for Nintendo Switch.
Players who purchase a physical copy of LEGO City Undercover on Nintendo Switch at retail are getting the complete game, and do not need to download additional content to enjoy the full experience. An internet connection is not required to play the game. The only internet connection suggested is to download the typical content update patch.
LEGO City Undercover releases for Nintendo Switch, PlayStation 4 and Xbox One on the 4th April. It is already available for Nintendo 3DS and Wii U.