No, I'm sorry, your understanding is not at all right.
In both cases, there is something he said or did that made you believe his profession is not teaching.
In the first case, you are thinking about him now. (He didn't object when you wrote "I seen it"? He must not be a teacher. -- Anyone who is a teacher would object. He didn't object, so I conclude he's not a teacher.)
In the second case. you are thinking about him at at time in the past.
In neither case is he likely to be a teacher soon.
Student or Learner