Re: Is phone a break for your brain ---- The real effect is that of "breaking away from" the task, so that your neural system and automatic systems have a chance to take over without interference from your conscious efforts.
I used to talk about this metaphorically with imagery. The imagery was this: You're working at the piano, and dumping packets of information into your "brain" like a big storehouse. Once you're done, these little elves and gremlins come along, carefully put all those packets into shelves, attach labels and connectors to them, so that the next time you work on piano, you've got this organized storehouse with everything connected, instead of a disordered pile of packets. The elves and gremlins are expert at doing this.
Maybe the story of elves, gremlins, and shelves seemed too silly and childish, though I actually do like thinking of it in this way. Maybe talking of neurons, neural pathways, synapses and such seems more serious. When I was first given the info, it actually did start scientifically with those kinds of terms. I translated it into elves and shelves because that worked for me. The bottom line is that there is a process, and if we try too tightly to control everything all the time, we can actually get in the way. In that sense, distraction via the phone might help, because instead of interfering with the process for that stage, you're busy chatting with friends or whatever. It's not a matter of "resting" but a matter of stepping away. (Thinking about this).