The Mahabharata ?'s

The film altered a little bit from the text when it came to Arjuna's son, Abhimanya, going into the circular array. In the movie he tells the others that he heard his father telling his mother, while he was in her womb, how to get into the array. Though he didn't hear how to get out. Abhimanya was begging the elders to let him go in so they could follow. He desperately wanted to help in the war, though they thought he was too young. In the book, the elders were urging him to go in, so they could follow him in for battle.

Why do you think Peter Brooks changed this aspect of the epic poem in his film?

Or is it because there is more to the epic poem that was left out of this text?