When departing from LHR/LGW at least, BA themselves have told us in the past that OLCI improves your chances of an OpUp because you have shown more intent to travel than someone who hasn't. They want to avoid upgrading someone who then doesn't show for the flight. This was before the DUT came into use, but I see no reason to think that logic would have changed, just the process for choosing from those who have checked in.