Why haven't the majors bought out Linc or Carbon Energy, in that case? Does it mean they think UCG is unlikely to work?
Incidentally, I'm sure the oil majors get up to all sorts of evil that we don't learn about but the suppressing-water-as-fuel conspiracy theory is tinfoil hat stuff. It's physically impossible to use water as a fuel without putting more energy into it than you get out, unless you have plans for a nuclear fusion device.