First of all, comparing a locked-down smartphone with a fully capable smartphone is different from comparing a smartphone with a 'landline phone'. That's like apples to apples compared to apples to oranges.

Secondly as far as I understand, you need the same type of phone at both ends to communicate with each other. Looks like the tin-can and other similar devices are designed to talk only to each other. While that is a restriction, it eliminates the avenue for a comparison. The friends are all on equal ground.

Thirdly, you're talking as if parental controls, especially unequal parental controls are a bad thing. Parental controls aren't like government or corporate restrictions. There is a necessary assumption that parents act in the best interests of the kids, unlike the other two.

Some parents are irresponsible and may allow their kids to consume alcohol or drugs. Will you allow your kids to do it too, because it may end up in comparisons? You have to talk to your kids about why that is a bad idea. It's wrong to assume that kids won't listen at all. Don't most kids refrain from drinking, smoking and driving till they come of age?

If this sort of control seems unfair or unethical to you, you're basically exposing your kids to serious dangers. And brain rot is a very serious problem that HN doesn't talk enough about. It ruins even the seniors. But for kids, it wreaks havoc with their IQ and personality.