The first time I encountered this was a purchase of vintage beads almost 20 years ago. I made necklaces with them. It took YEARS for the coating to chip off! (Opaque white glass underneath.)

I had to restring some customers' necklaces for years after.

So even if you etch them, there's no guarantee the coating won't fail later.

I would imagine tumbling would simply remove the surface of the coating and make it even more vulnerable to peeling/chipping off.