::: No, it is not "incorrect" to have nicknames.  The article does not imply that "British Open" is the official name, just a nickname.  The British often refer to the event as "The Open", which by your logic is just as incorrect.  However, that is a perfectly valid nickname, as is "British Open" for others.  The official name is The Masters Tournament, but it is generally referred to here as just "The Masters", and sometimes outside the US referred to as the "US Masters" .  Neither is "incorrect", but are nicknames that make more sense from the speakers' perspective, for whatever reason.