Couple of things with that.

The simulator was in a town, not a highway.

The drivers given the alcohol were given the legal limit. Every drop more than that would impair more.

Texters were given long messages to read & write. Not quick burst messages that can be typed without looking at the phone.

Separately the page notes that 74% of people asked said they would use Facebook while driving. Yet only 10% of accidents are from distraction, and only a small percentage of those distracted, were distracted by a phone. With changing the radio station being a bigger cause of distraction related accidents.

While, 4 million (1.8%) US drivers admit to drink driving at least sometimes. Yet 50% of fatal highway accidents are cause by drink driving.

So yes, while doing long texts of messages you are being asked to remember, in city driving, may impair your reactions more than someone at the legal limit of alcohol. Texters are statistically nowhere near as dangerous as drink drivers.