> Is it expected that a fact checker contact everyone a journalist interviewed and go over each sentence and claim line by line and verify that it is true? Yes

> Is it expected that a fact checker contact everyone a journalist interviewed and go over each sentence and claim line by line and verify that it is true? Yes, this is exactly what fact checkers at top newspapers were traditionally paid to do. I have no idea how many true fact checkers are left, but you described the job precisely.