Probably depends on the type of screen. iPhones and iPads? I doubt it matters in the end, one way or another. Those things are incredibly intuitive and a monkey could learn to use it.
Traditional computers? I think it does make a difference. They're certainly amazingly easy to use compared to the old command-line computers of the 80s and before, but I see gaps in literacy everywhere depending on exposure.
My kid is 10 now, and I've never really paid attention to "screentime" when he was younger. I mean, I wouldn't let him waste away for hours on Candy crush like a zombie everyday, but I genuinely don't mind if he binges on cartoons or his Xbox or the PC so long as he keeps out of trouble, maintains his grades and relationships with us and his friends, behaves well and doesn't pack on the pounds. He has his own desktop. He's had his own smartphone since he was 8. His own tablet since he was 6. His own console since he was 5. Only thing he doesn't have is a TV in his room, and that's largely because there's no room. Some of you are probably reading this and thinking I'm insane.
He is by far the most digitally literate kid his age I know. The other day, the Wifi went out while he was home alone playing Xbox (I was running a quick errand to the convenience store across the street). I came back in and he was troubleshooting it on his phone, and fixed it. Turns out he needed to open up the Network ports on our router because a power surge reset the settings. He can type at 60 words per minute. When our TV started acting up (the speakers broke), he immediately knew how to navigate the menus and change the settings to have the sound pop out of the TV speakers.
His neighbor friend, who is 9, has been kept away from computers her whole life and doesn't know what the difference is between a modem and a router, and she needed my help at my place to turn on the computer, because she didn't know that turning on the monitor doesn't turn on the computer because her parents hovered over her for her "30 minutes of computer time". And oh my god, she types so. freaking. slow. She still "hunts and pecks". I'm sorry, call me a judging asshole, but I find that pathetic. Not to mention that she is so awkward. My son can't connect with her (and it's not because she's a girl, 4 of his 7 core friends are girls), because when he makes references or jokes to TV shows or video games or things on the internet, she just stares at him like an alien and doesn't know what he's talking about. I find it very ironic that the screen immersed 10 year old boy I'm raising is far more sociable than the awkward 9 year old neighbor who's never picked up a controller in her life. So much for the "screens ruin socialization skills" argument.
To be frank, I'm always stunned when I come on here and I see how strict parents are with screen time. Like, holy crap, no offense, but as someone who grew up playing hours of Nintendo every day from the time I could pick up a controller and watching Saturday Morning Cartoons from 8am-Noon every weekend from the time I was 3, I'd have hated to be a kid in some of your homes. An hour a day? 30 minutes? Holy shit. Are some parents really that inflexible?
That's barely enough for one freakin' level of Halo, my favorite game as a kid. The Mass Effect trilogy, my favorite game today, takes 120 hours to get through. It's barely enough for a single full episode of hour long shows shows. What about movies? Are they never allowed to watch movies? Or do they have to "bank" it up? I was allowed to just put on a movie whenever I wanted as a kid, so long as had the time and wasn't grounded. I'm just so confused.