It's true! From the Starbucks website:
"When you use your registered Starbucks Card or Mobile app to purchase any handcrafted beverage and then present that same Starbucks Card or Mobile app, you can get free refills of brewed coffee (hot, Iced Coffee or Cold Brew), and tea (hot, iced or shaken) during the same store visit at participating Starbucks stores."
So next time you have to hunker down with some work or a good book, venture out to your local shop and drop $2-3 on a drip coffee, then sit and sip all. day. long.