Deathly Hallows Part 2 hangar à bateaux, remise à bateaux set photos

okay so toi know how toi can only see thestrals after toi have seen death? well how come at the end of the fourth book after harry sees cedric die, it still says that the carriages were pulling themselves? he cant dee the thestrals until the beginning of the fifth book when school starts, but not at the end of the fourth book when school ends. its confusing...does anybody have a way to ask jk rowling about that cos i suck at finding adresses and stuff like that. has anybody noticed that, ou am i just a freak who reads the livres too many times (about seven times each) and too carefully....oh well i dont really care... i l’amour hp!