A asked, 'he did say he would be here by 4?'
If... if - B says No, he didn't say that.
then B is disagreeing with A - David did not say he would be there by 4.
logically, B does not have any expected time of arrival for David. So how can he then say, 'he must be delayed/late'? Only when you expect someone to arrive by a particular time, and then they don't arrive, can you say 'they are delayed/ they are late'.
Student or Learner