It's a test for proving that chimpanzees have a better short term memory than humans. It's inherent to their survival instincts in surroundings which require constant alertness. Something which we have lost a long time ago, because it was no longer required.
And even in lab environments, this capability remains so it seems. Chimps learn, and pass on their knowledge from generation to generation. Quite a remarkable animal.
The memory test is a piece of cake for the chimp. Any order, it doesn't matter, it can resolve the puzzle in a matter of seconds. If not faster.
We have to study the information first, absorb it. It takes longer. A lot longer. Even so, we only get half (at max) correct.