I had a friend back in university who's parents did the same. Completely locked down with no internet access unless it was explicitly with her parents observation well into her late-teens. She found freedom when she went away to university, and with that freedom she didn't know how to regulate it. She'd be up all hours of the night scrolling everything shes missed in years past. Games, pop culture references, ancient memes, hours and hours of YouTube playlists, etc. It affected her schooling to the point where she almost withdrew because she'd be so wrapped up in the internet, she wouldn't know how to time-manage for completing assignments or even getting to class. Needless to say her inability to impulse control caused quite a few GPA scares and a lot of money spent on off-term sessions. I remember we agreed as an apartment to put a parental control pin on the communal Xbox because she'd sit for hours and skip class to play.
I can't quite say all this is related to her parents essentially banning her from technology, but it certainly changed my view on how I'd introduce my child to the internet. We're coming to view internet addition similar to drug or alcohol abuse; and I think any sort of responsible moderation that can be learned as a child continues as skills into adulthood.