It's already available on older Androids (my stock Android 6 Nexus 5 has it).

It asks to enable it on a per Wifi basis, if it detects any traffic is being mitm mangled, and you have to agree to enabling it for that Wifi.

I don't know if it is on by default but if enabled it will connect to "High Quality" open networks. If it does this it connects the VPN.

So the VPN is "required" by this feature but you can turn it off globally, or manually connect to networks where you don't want to use the VPN.

Doesn't this violate the computer fraud and abuse act, for unauthorized accessing to a networks without permission? More specifically, piggybacking [1]?

[1] https://en.wikipedia.org/wiki/Legality_of_piggybacking