This is True Shooting %. It starts with effective FG%, which takes regular FG% and incorporates 3's made and attempted (if 2 players have the same FG%, the one that makes more 3s has a higher effective %). True Shooting % also incorporates getting to the line and FT%.
There are flaws with this statistic, like all others, but I think it is a better measurement than using FG% and 3 pt FG%, because you cannot tell what % of the player's overall shots are 3s (the higher that is, it will dilute the FG%). This also includes how often you get to the line and how effective you are when you do, which are also important criteria.
One aspect that needs to be pointed out in defense of some of the low FG% shooters is that they often have the ball as the shot/game clock winds down. Also, teammates are less willing shooters and therefore there is defensive help on the primary shooters. This often leads to hockey assists as they swing the ball to avoid the double-teams.
Lastly, even though we are generally all big fans of Karlie and her sister and her lead over 2nd place is enormous, it's still a little easier for players who don't play as many minutes and are not the primary option (from a defensive perspective as well) to have a higher FG% of any type.