Are there not hydrogen rich microzones (volcanic fissues? atmospheric layers?) where these might thrive?
I'm not actually worried about bugs taking over the world. But we ought to avoid hand-waving away possible unintended consequences, because that tends to be how we get ourselves into environmental problems in the first place.
While there are certainly conditions in which these bacteria might thrive, their inbuilt inefficiency -- secreting large quantities of energy-rich alcohol -- suggests that, in their current form, they'd be relatively easy to outcompete. They don't seem to have any particular advantage in an environment where their unique characteristics are not beneficial -- and very few environments would seem to fit that bill.
I'm not actually worried about bugs taking over the world. But we ought to avoid hand-waving away possible unintended consequences, because that tends to be how we get ourselves into environmental problems in the first place.