The last sentence in the article explains that they compared the tools to others collected from Australia, which must have been used for similar purposes, and f

The last sentence in the article explains that they compared the tools to others collected from Australia, which must have been used for similar purposes, and found much more variation between African and Australian than between African tools from different places. I.e., this is not a question of convergent evolution. There is more than one way to skin a cat or thylacine. What we see here is path dependence. Tools were made a certain way because one's father, grandfather, and great-grandfather made them that way and reproduced successfully, and not because that was the only way to make such a tool. And, people who had previously made tools differently, or did without, adopted these, and maybe abandoned others. Maybe these were superior, or maybe people using them had more social cachet, prompting emulation; either way, the design was learned, so communicated.