It’s not the critical mass as such that does it, but the mass of high explosive arranged to give a spherically symmetric shock front to compress the fissile material. So if one uses another means — I thought the article mentioned lasers, though I’ve never heard of lasers reliable enough to ignite/sustain a fusion *explosion*...much of the weight requirements go away.
Too tired; need to explain. Right now fusion weapons are triggered by the temperatures achieved during a fission explosion first. So you need the uranium/plutonium to have a fission reaction; the liberation of neutrons + the temperature, kick off the fusion reaction of the H-bomb.