How much of this is just timing though? Anecdata, but my parents took my computer away a bunch of times and restricted me from watching TV on weekdays, and I still got terrible grades in middle and high school (though I almost always did well on tests, just didn't like doing homework).

My grades didn't get measurably worse when I got the computer back, and my parents stopped taking it away from me when they saw that I was teaching myself how to code for fun, because I think they realized that is a marketable skill, and I think I taught myself to code (and my grades started improving) because I simply grew up a bit.

Granted, there weren't really "smartphones" throughout most of my high school years, and I didn't even have a laptop at that point either, so it's possible my information is out of date.