Earlier quoted context omitted.
So, they could use computer only on weekends. How your kid could become, for example, programmer? Where would you be if you would be treated as that?
According to their rules, "screen time" is not equivalent to "using computer". It seems like a reasonable way to limit unproductive, pure-entertainment computer use. A parent with some common sense should be able to identify what is productive.
I also expect these rules to change along with the kids, not remain static. If we're successful, then by 16 or so I expect that the rules will be down to "Don't wake up sleeping people."