I assume by competent he means knowing the steps, how to lead or follow, and other basics. Kind of like how you can learn how to move the pieces in chess and learn basic strategy in a few months. You can get good enough to be better than 95+% of the population. You may set the bar for "competence" higher, but it's not a facially crazy assertion. That said my dance knowledge ends with a box step and I would definitely not call myself competent.