I'd say, not "people in general" but people form other socioeconomic strata. This guy is not talking like us, suspicious. He talks in an elaborate and thought-through manner, not simply, so, he's not candid, double suspicious!
Not necessarily but it carries less weight than pre-LLMS. Obviously it's just a heuristic and not the whole story and telltale AI signs are not purely about good spelling and grammar. But I just appreciate some natural, human texture in my correspondence these days.