Even though handsfree is better than touching your device while driving, voice interaction can still be distracting. Checking to see whether the device properly understood or transcribed can mean squinting and shifting focus off the road to the screen.
Texting is an act that is much more than just putting a finger on a device. It’s thinking about what to write, the tone, then composing first in one’s head and then inputting, followed by proofreading and then transmitting. None of those things are defensive driving.
Better that we don’t reply to any messages while on the road, even by voice. Better still that we all use autonomous driving.