There was a short period of time, around 2002, when they were doing some experimental studio sort of pieces, in limited editions. Many of these do have layers of tiny controlled bubbles in them towards the base, just like this and I imagined your vase might come from that time, given the book does say that they did the Barrels in more colours, later on, why would they not have decided to try a layer of bubbles in a Barrel when they were introducing them into other things anyway?
It seems a perfectly logical thing to try.

I can remember the pieces coming up for sale in posh gift shops and department stores, around the same time as Alchemy. All the shelves had big notices on them telling customers "not to touch". You had to ask for permission to see a bit - even of Alchemy.
I suspect the limited edition studio things were just too expensive to be commercially viable.