It isn't nit-picking. It is actually an important distinction. Laws vary from state to state. In fact, there are a number of states that permit a parent or guardian to serve alcohol to a minor in a restaurant. And many more states that allow a parent or guardian to serve alcohol to a minor on private property. It so happens that Florida does not allow either of these. So the advice provided above is correct as it pertains to Florida. But it is both incorrect and misleading to suggest that a 19 year old cannot consume alcohol with their parents
in the U.S. because there are states where this is perfectly legal.
In case anyone is interested, here is a source that shows where each state stands:
http://drinkingage.procon.org/view.resource.php?resourceID=002591