If the tools found at Jebel Faya were different to those found in Africa, why would this mean that the two groups of humans using these tools were probably different?

Reverse reasoning

Explanation:

It is acclaimed by scientists and researchers in Jebel Faya (Arabia) that the stone tools found there are very similar to the ones found in East Africa. They reasoned that this showed that the tools were used by the same people who emigrated from Africa to Arabia, somewhere between 100.000 and 60.000 years ago. This emigration is an accepted fact; the archeologists differ in when exactly did this happen.

Now when the stone tools found in Jebel Faya would have been different to those found in Africa, you can reason in reverse and come to the conclusion that the human groups were different.