The Fondation Prince Pierre was established by Prince Rainier III of Monaco in February 1966 to promote culture and the arts through the creation and the awarding of prizes. Prince Rainier III created the foundation in tribute to his father, Pierre de Polignac a great patron of the arts.
Prince Rainier III's foundation is a tribute to his father, so it must support the arts. 
His father, it was specifically mentioned, was a great patron of the arts, and this foundation is a tribute to him. The ambiguity in stating that it supports the arts because it's a tribute to him made the AI consider that it's not classified as true or false.