How does he explain the existence of shale oil? If his theory is correct we would only expect to find oil in association with igneous or metamorphic rock.
That being said, I have long suspected that the biosphere extends much farther down into the crust of the Earth than anyone would ever believe.
I once wrote a science fiction story (unpublished and unpublishable) wherein, billions of years from now, the Earth is a frozen lump circling around the white dwarf star that Sol will become. Several teams of hyperevolved humans come and drill through the thick ice, and then through the cooling crust, to create geothermal vents that will melt small regions in the deep ice, where they can nurture designed ecosystems. The idea is that, after the ecosystems have evolved for a time, enough vents will be drilled to create a single ocean under the deep ice, in which the ecosystems will duke it out for supremecy. The team whose designs prevail will win the planet.
You can probably guess the ending. One of the vents goes deep enough to reach living native organisms, still reproducing in the dwindling warmth of the Earth's core. The native organisms outcompete all of the candidate designs, and the Earth, itself triumphant, is left to evolve on its own.
God knows the ending...the beginning...the reason. Not us.
"...the Earth, itself triumphant, is left to evolve on its own."
HAH! I don't think so...