On this site, only the NHL, the Pac 12 North, and the Premier League have records entered for (a sample set of) the teams. The shortcode displays only the three teams with standings to show.
No records found in league testus-maximus.
If you wanted to show all the leagues in the drop-down, you could use this simple(r) incantation:
NOTE: only use ONE instance of this shortcode on a given page. Otherwise you will see some strange behavior.