Plasma isn’t all that rare or weird, it’s just ionized gas. Flame is a plasma, e.g. Glowing gas of any kind is a plasma.

So there are all levels of energy possible, and an ionized miniature donut of “ball lightning” is many orders of magnitude less energetic than plasma creating or “hosting” fusion processes, and consequently much easier to contain and stabilize. I haven’t seen their projections, but it seems implausible that they can “ramp up” what they’ve got to the necessary levels.