Solis though... Solis is bored and curious. Curious about Vernon and Petunia's reactions to the letters. Harry getting mail is weird by itself, but them trashing the envelope before seeing its contents is even weirder. It's like they knew immediately what was in it, and that makes Solis" curiosity grow. The black-haired boy can tell the adults are on edge and after Vernon's jab at him that morning of being Dudley's "placeholder for college scholarships", Solis wants to poke the bear. And what better time to disclose that he too got a letter?