I've been in planetary science and never encountered this theory. I have a default position of skepticism towards it for that reason, but I don't have a reason to object on the face of it. The question is not where the oceans came from (that's settled -- it came out of the mantle as the Earth cooled, and ultimately before that from cometary impact), but how the oceans did not boil or evaporate off like they did everywhere else. I could understand a theory that they were kept from boiling by being in the habitable zone AND by some combination of life processes, and that this hydrogen-capture mechanism helped replenish the ocean as hydrogen escaped from natural gas upwellings. But I have no sense of the scales and magnitudes involved to see if inputs approximately match outputs without seeing the underlying paper.