Frankly, I don't buy it. If we have a problem with detaching from technology, then, stopping all usage of it only one day a week is maybe 90% as unhealthy.
It would be like saying you have a healthy relationship with smoking because you don't smoke at all for one day a week, but after that you can chain smoke 24/6.
Now, I definitely don't think that social media/technology/<modern_thing> is nearly as bad as smoking. But if we accept the premise that maybe we're using it too much, then I think it's delusional to believe that stopping it for just one day a week is going to do anything substantial.