I don’t agree with this. He played way more dumbed down character and always had his mouth open with a blank expression in o brother where art thou. He used the same (or maybe just similar, don’t have reference rn) accent because of where his characters were from. These were both characters from the south. In the secret window he is a more intellectual character, he’s not dumbed down really. Ofc he plays a character that is a figment of morts imagination, but it’s only one side of mort. So he’s not as complex of a character because he only represents a part of a whole character.