If that were true, how do explain studies (like this one) that show that hands-free devices also hurt reaction time worse than alcohol? Drivers don't even need

If that were true, how do explain studies (like this one) that show that hands-free devices also hurt reaction time worse than alcohol? Drivers don't even need to "let go of the phone". They're looking straight ahead, and they have to respond to a big red rectangle, right in their field of vision. Yet somehow, they're still worse at it than people who have been drinking.