Why does Baldwin choose not to present the events in a strictly chronologicsl order?
This is a great question that has a lot of history to its answer.
Baldwin is a contemporary writer. Before WWI, we had what is called the Victorian and Edwardian ages of literature (Dickens, Austen). These stories are always in chronological order. This is because the general belief at the time was that history is progressing always. The philospher who first said this was named Hegel. He said that we are on an onward march toward human progress.
Then WWI happened and everybody freaked out! (That is the colloquial version.) Authors started to write less linearly and more fragmented because they didn't feel like narratives need to be linear any longer. We were supposed to be progressing, but now we have a giant war. Everything is meaningless! AH!
So we move into the Modern era of literature (1915 to the 1960s). The best way to tell if a work is a piece of Modern literature is to check if it is fragmented (i.e., if it jumps around). Baldwin wanted his story to feel like it was from that era of literature.