first, let me tell you what just happened in this scene:
Grand Pabbie tells Anna that there’s ice in her heart and tells her that only an act of true love can thaw a frozen heart. Then, Bulda suggests, “a true love’s kiss, perhaps?” And then Kristoff says that he has to get Anna back to Hans (so he can kiss her and thaw her) and then they go. Then it shows Olaf and he says “I’m coming!” AND IF YOU LOOK IN THE BACKGROUND YOU SEE GRAND PABBIE DOING THIS. It kinda looks like he’s saying “no” and reaching his arm out. I interpret this as him saying, “No that’s not what i meant, i didn’t mean a true love’s kiss, i meant AN ACT OF TRUE LOVE.” Grand Pabbie never said it meant a true love’s kiss, Bulda suggested it and the trolls kissed each other. GRAND PABBIE KNEW THAT ANNA HAD TO DO THE ACT OF TRUE LOVE HERSELF. HE KNEW. We know that he can kind of see the future and stuff and we know that he can tell a lot from a person just by taking their hand and looking at them. Because of all this, I’m pretty sure that he knew that a true love’s kiss from Hans wouldn’t save her. And it’s also possible that he knew that Hans was evil. But Anna and Kristoff left before Grand Pabbie could say anything.