Thanks for the info, although I never would have bought without knowing more.
If the pH of the water increases, it means that there is a "base" type product in the beads, so that it would not be just ceramic. And that this product would not end up being lost by the marbles. It would still be chemistry. Ph cannot increase without supplying a variety of ions other than H / OH.
Probably the beads are useless but if it is not too dirty, washing with pure water can give the illusion that the job has been done well and deceive people.
It smacks of a scam.