: (we know that stock Dwarves can repair
: world knots, why wouldn't more accomplished dwarves be
: able to supply fellow troops on the field with bottles
: via the same or similar magic?).
I have to say that the dwarves we had on Force Ten From Stoneheim were not stock in any way. In the journal entry for that level, they are referred to as "Dwarven Irregulars". However, they could still be standard dwarves but just not part of the Legion.
They may have been called from Stoneheim itself, as the level name suggests, which in turn may point to the city still being in the hands of the dwarves. If this were the case, I would imagine they are experts in World Knot affairs and were called for this specific mission. Otherwise, they may have been required only because the Legion did not have enough dwarves to spare for such a mission but I doubt this is the case.
The first possibility allows for there to be World Knot experts within Stoneheim. It also means that the dwarves aren't trapped there. Whether they can leave through World Knots or out a secret entrance is a different matter though.
