Except Calvinists believe in unconditional election before the foundation of the worldlol!
Had given and have given are two different groups. Jesus was at that time speaking only about the disciples that were then following him. The world could therefore include those who would be given but had not yet been given. It has nothing to do with "Calvinist belief" and everything to do with proper exegesis.
so all the elect had/have been given to Christ
Now if you want to deny all the elect have been given to Christ according to unconditional election before the foundation of the world then I would agree with you
BTW I do agree in the context those who were given are the apostles
The point however is world does not mean elect in that passage or any other in scripture