Unfortunately that was a flawed study. They paired trained chimps with people who saw the task for the first time.

It was later repeated, and if given the same training, humans still outperform chimps in this task.

Any source?

Edit: Answering myself: https://gwern.net/doc/algernon/2009-silberberg.pdf

However,

* we see no videos of the two men doing the test. Notice how the ape barely looks at the task, while the men maybe were highly concentrated.

* The men had the goal to improve and beat the ape, the ape probably did not have that goal.

* The men created the circumstances themself, so it may be possible the knowingly or unknowingly gave themself better conditions than the ape.

* The men did up to 2500 units of training, it is unknown how much the ape got.

* We can see that the ape does nine numbers in some tests, the men did just five.

* the men propably relied on language to learn the task, the ape did not.

So, this is quite a flawed study too.