While we didn't just hand my son a device, the reality is he grabbed our phones at 1 year and played with it. Even in those quick grabs, it was intuitive enough to watch him play with pulling down the notification drawer or tapping on things. I would say that's minimal interaction but certainly a different level then someone who plops a 1 year old in front of an ipad or one that has no electronics in the home.
To elaborate on this, very young human beings have a fascinating aptitude for figuring things out. They aren't very good at it, or at least lack the motor skills to apply what they learn, but you can tell that there is a lot of cerebral activity happening as they try to puzzle things out. So when a puzzle presents itself, such as "why is mom staring at this glowing rectangle so much?" they will will want to try and find out why.
My 1 year old twins have been trying to play with my wife and I's phones since they were old enough to start grabbing stuff. They also make for great little distractions during diaper changes when they'd otherwise try to sit up or flip around. We usually lock the screen before we let them play with the phones, but occasionally I'll let them swipe and tap around just to see what they can figure out.
I imagine (though the full study hasn’t been published yet to check) that they recruited children that already had X amount of touchscreen usage each day. I very much doubt they forced children into different brackets of touchscreen use as part of the study.
Nobody knows, but it happens and so we should research the effects.