My understanding is that they are using molten metal fluid...

My understanding is that they are using molten metal fluid reactor pyrolysis to split methane creating hydrogen and solid graphite. As this process requires some serious temperature they are combining their Sibox tech to save some energy. This could be helpful because heat loss as temperature rises is not a straight line graph. Insulation at lower temperatures (ambient to 600C) is modest, over 1100C it requires more than double the energy input so it quickly becomes very expensive. There'd be no point in creating hydrogen if the energy to make it exceeded the energy the hydrogen could produce, unless the graphite product profits were high.