If I'm understanding the study correctly, it's not that having one of these systems in your car results in you — at all times — being more distracted than if you had pot/alcohol in your system. Rather, when you are actively engaged in a task (eg, play song on Spotify), you are worse at lane centering and maintaining follow distance.
That is not as bad because you can choose when to start playing a song, so that you do it when traffic is calm. If you're driving under the influence, that's affecting you the whole time.
It would be interesting to see how these results look when the driver is performing tasks on a non-touchscreen setup. I can easily change the radio station in my car using steering-wheel mounted buttons, but changing the AC/heat is quite difficult without looking (in my Ford CMAX) because of the uniformity/location of the buttons. I'd guess the results would be similar to using a touchscreen setup.