Harry and the thestrals

Ok can someone please explain to me how Harry sees the Hogwarts carriages as horseless in the end of GOF, but then can see the thestrals pulling the carriages in the beginning of OOTP? I always thought he could see them now cuz he saw Cedric die, but I recently listened to the new audiobook and noticed two things—

1. When Cedric dies Harry’s eyes are closed, so he doesn’t actually see it happen.

2. When Krum comes to say goodbye at the end of the book Harry sees the carriages as horseless.

Am I missing something here?