I think the consens is DMT is also present at physiological conditions in ionic state inside of the bark.
But I think for these hot pressing methods it would not matter, they seem to just liquify any kind of alkaloids and terpenes and press them out at increased temperature due to the high pressure.
I have no clue of this stuff, but I just knew people do it for cannabis. That would make me wonder if it the bark starting material compared to the flowers of weed would not be the problem here. First ones are strongly lignified, high crosslinking density and not really flexible at all. Can't really imagine that you could squeeze that material like a sponge.
But in case those Kava roots exhibit roughly the same morphology then maybe there is a chance?