The article is too good to focus on tiny "mistakes". Instead we should value everything you dug up and presented as a convincing read.

It would be of (my personal) interest to know how the work, how the carving was done in detail - where, when and how, with the help of what kind of tools, they have been able to create this (often very intricate) PF-beads?

I personally believe this work was done in Mauritania for the most part. Most likely in the few pockets of Berber (Zenaga/Sanhaja) settlements in the country, possibly by the same folks that crafted the carved shells.